Light guide plate, lighting illuminating device using same, area light source and display

ABSTRACT

A light guide plate includes (i) a first light guide layer made of a material having a refractive index n 1 , and (ii) a scattering light guide layer having a function of scattering light. A reflection means for irradiating the scattering light guide layer with the light having propagated in the first light guide layer is provided on a surface opposite to a light guide surface of the first light guide layer, the light guide surface on which the light is incident. The scattering light guide layer includes at least (i) a second light guide layer made of a material having a refractive index n 2  (n 2 &lt;n 1 ), and (ii) a scattering layer for scattering the light propagating in the second light guide layer.

TECHNICAL FIELD

The present invention relates to a light guide plate and a lightingapparatus capable of changing light from a point light source or alinear light source into a planar light source.

BACKGROUND ART

In recent years, semiconductor light sources, such as LEDs (LightEmitting Diode) and LDs (Laser Diode) has been significantly improved inperformance, especially in luminance and luminous efficiency. Inaddition, the semiconductor light sources originally have advantages,such as high color purity and a long life. Therefore, the semiconductorlight sources are being utilized as a light source of illumination.Especially, in comparison with conventional light sources, thesemiconductor light sources can increase color reproducibility. On thisaccount, application of the semiconductor light source to a backlight ofa liquid crystal display, an electric poster, or the like has attractedattention.

However, because of the low color rendering property (colorreproducibility) of a white LED, a backlight using a light source ofwhite LED is not frequently used as the light source of generalillumination. The white LED is rather used for creating a goodatmosphere, or for something which do not require high colorreproducibility, such as tail lamps of cars.

In order to improve the color reproducibility, proposed is an art ofconstituting a lighting apparatus with a light source having a pluralityof different monochromatic lights, such as a plurality of LEDs.

However, in order to produce a planar light source for the backlight ofliquid crystal display, the electric poster, etc. from the point lightsources, such as the LEDs or the LDs, a process of producing planarlight source and a process of mixing colors of R (red), G (green), and B(blue) are necessary. The following explains a concrete example.

As shown in FIGS. 23 and 24, in a first conventional art, the process ofproducing planar light source and the process of mixing colors arecarried out by separate light guide plates 301 and 300. LEDs 304 of R,G, and B are used as the light source. Light having been emitted fromthe LEDs 304 first enters into the light guide plate 300 used for colormixing, and three primary colors of R, G, and B are mixed while thelight is being guided. As a result, the light becomes substantiallywhite. Next, the light is turned back by a prism 302, and enters intothe light guide plate 301 used for planar light source producing. Thislight guide plate 301 used for the planar light source producing isnormally made with a process of applying reflection dots 303 onto a backsurface of an acrylic flat plate. The light is guided by internalreflection in the light guide plate 301 used for the planar light sourceproducing, until the light reaches the reflection dots 303. Bycontrolling a distribution of the reflection dots 303, it becomespossible to easily adjust surface luminance uniformly (see Non-PatentDocument: Program Book of Color Forum JAPAN 2002 hosted byKOUGAKUSHIGAKKAI, page 95).

Next, as shown in FIG. 25, in a second conventional art, the process ofproducing planar light source and the process of mixing colors arecarried out by a single light guide plate 305. A light incident side ofthe light guide plate 305 is thin while the opposite side is thick andshapes a wedge. An LED 306 of R, G, and B is used as the light source.The light enters into the light guide plate 305, and proceeds by totalreflection. As the light of RGB is proceeding toward the other side inthe light guide plate, the colors are mixed. An oblique reflectionsurface 307 is provided on an end surface of the light guide plate 305,opposite to another end surface close to the LED 306. The obliquereflection surface 307 changes the angle of light. Then, while the lighthaving been reflected by the reflection surface 307 is proceedingtowards the light source, its incident angle with respect to an innersurface of the light guide plate 305 becomes larger. When the incidentangle becomes larger than a critical angle at a position A, the light isemitted from the light guide plate 305. A reflection plate is providedat a surface (back surface) of the light guide plate 305, opposite tothe light emitting surface, and an airspace is provided between the backsurface and the reflection plate. Therefore, the surface luminance isadjusted by a shape of the reflection surface 307 (see Non-PatentDocument 2: Gerard Harvers lumileds [online], searched on Dec. 18, 2002,the Internet <URL:http://www.lumileds.com/pdfs/techpaperspres/SID-BA.pdf>, page 21).

However, these conventional configurations have the following problems.

In the case of the light guide plate described as the first conventionalart, the planar light source producing and the color mixing are carriedout by separate light guide plates. Thus, each light guide plate has tohave an enough thickness for producing the planar light source or mixingthe colors, so that the thickness and weight of the resulting lightguide plate are doubled. Moreover, light conductivity may be reduced bylight loss in the light guide plate connection section, which connectsthe light guide plate used for the planar light source producing and thelight guide plate used for the color mixing.

Moreover, in the case of the light guide plate described as the secondconventional art, the designing of the light guide plate (for example,reflection surface) is extremely difficult if attempting to achieve anuniform surface luminance. For example, a light guide plate of a 20-inchliquid crystal display with a screen length of 300 nm has a thickness ofonly a few millimeters. With such a thin plate, the entire luminancedistribution needs to be controlled in a narrow region. In this view,practical use of the second art is not likely. Further, even a slightchange of light distribution due to variations of components andununiform assembling may change surface luminance distribution.Therefore, mass production of the light guide plates is difficult if thesame quality is required.

DISCLOSURE OF INVENTION

In order to solve the above problems, an object of the present inventionis to provide a light guide plate capable of converting a point lightsource and/or a liner light source into a planar light source, whichlight guide plate is made with a smaller thickness than the conventionalplate, and allows easy mass production. The light guide plate of thepresent invention with such advantages is constituted by stacking aplurality of light guide layers whose refractive indices are differentfrom each other.

In order to achieve the above object, a light guide plate of the presentinvention includes: a first light guide layer on which light from alight source is incident, made of a material having a refractive indexn1; and a scattering light guide layer for emitting, as scatteringlight, light incident on the first light guide layer, the first lightguide layer and the scattering light guide layer being stacked on eachother in a direction orthogonal to a direction of light propagating inthe first light guide layer, wherein: the scattering light guide layerincludes at least (i) a second light guide layer made of a materialhaving a refractive index n2 lower than the refractive index n1,adjacent to the first light guide layer, and (ii) a scattering layer forscattering light propagating to the second light guide layer; and thefirst light guide layer includes, on a surface opposite to a light guidesurface on which the light is incident, reflection means for reflectingthe light propagating in the first light guide layer so that the lightis incident on the scattering light guide layer.

In the above arrangement, the first light guide layer and the scatteringlight guide layer are stacked with each other. Substantially all thelight beams having been incident on the light guide surface of the firstlight guide layer proceeds forthright, while repeating the totalreflection, in the first light guide layer until the light reaches thereflection means. Then, the light is reflected by the reflection means.The light having been reflected is incident on the scattering lightguide layer. More specifically, the light having been reflected by thereflection means is incident on the second light guide layer, and thenthe light is incident on the scattering layer. The light having beenincident on the scattering light guide layer (scattering layer) isemitted as the scattering light. In this case, the second light guidelayer only has to guide the light to the scattering layer, therefore,the second light guide layer can be very thin. Therefore, for example,the thickness of the light guide plate can be reduced as compared withthe conventional arrangement in which the color mixing and the planarlight source producing are carried out by two separate light guideplates. Moreover, unlike the conventional arrangement in which the colormixing and the planar light source producing are carried out by onelight guide plate, for example, it is not necessary to finely design theshape of the light guide plate. Therefore, the light guide plate can bemanufactured easily as compared with the conventional art, so that it ispossible to mass produce the light guide plates. Note that, the lightpropagation direction in the first light guide layer here denotes not adirection of local light propagation but the light propagation in theentire first light guide layer. That is, the direction of lightpropagating in the first light guide layer denotes the way from thelight guide surface to the reflection means.

Additional objects, features, and strengths of the present inventionwill be made clear by the description below. Further, the advantages ofthe present invention will be evident from the following explanation inreference to the drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a side view showing a schematic arrangement of a light guideplate and a lighting apparatus in one embodiment of the presentinvention.

FIG. 2 is a perspective view showing a schematic arrangement of thelight guide plate and the lighting apparatus.

FIG. 3 is a graph showing distribution of light of an LED.

FIGS. 4(a) and 4(b) are graphs showing distribution of light of an LED,the light having passed through an optical element. FIG. 4(a) showslight distribution in a direction horizontal to a light guide surface.FIG. 4(b) shows the light distribution in a direction perpendicular tothe light guide surface.

FIGS. 5(a) to 5(c), are graphs showing distribution of light having beenincident on the light guide body. FIG. 5(a) shows distribution of lighthaving passed through a cylindrical lens. FIG. 5(b) shows distributionof light having been incident on the light guide surface. FIG. 5(c)shows distribution of light having been reflected by a reflection means.

FIGS. 6(a) to 6(d) are side views showing distribution of light havingbeen incident on the light guide plate. FIG. 6(a) shows propagation oflight having been incident on the light guide surface. FIG. 6(b) showspropagation of light having been reflected by the reflection means. FIG.6(c) illustrates a substantial part of light guide plate, showing anangle of light that underwent total reflection at an interface of afirst light guide layer and outside. FIG. 6(d) illustrates a substantialpart of the light guide plate, showing an angle of light that underwenttotal reflection at an interface of the first light guide layer and asecond light guide layer.

FIG. 7 is a side view showing a schematic arrangement of a light guideplate and a lighting apparatus in another embodiment of the presentinvention.

FIG. 8 is a side view showing a schematic arrangement of a light guideplate and a lighting apparatus in still another embodiment of thepresent invention.

FIG. 9 is a side view showing a schematic arrangement of a light guideplate and a lighting apparatus in still another embodiment of thepresent invention.

FIG. 10 a side view showing a schematic arrangement of a displayapparatus in still another embodiment of the present invention.

FIG. 11 is a side view showing a schematic arrangement of a conventionaldisplay apparatus.

FIG. 12 is a side view showing a schematic arrangement of a light guideplate and a lighting apparatus in still another embodiment of thepresent invention.

FIGS. 13(a) and 13(b) are side views showing a schematic arrangement ofthe light guide body. FIG. 13(a) shows an arrangement in which thereflection means is curved. FIG. 13(b) shows an arrangement in which thereflection means is projected in a direction of the light guide surface.

FIGS. 14(a) and 14(b) are side views showing a schematic arrangement ofa lighting apparatus in still another embodiment of the presentinvention. FIG. 14(a) shows an arrangement in which a convex lens isprovided near a light source. FIG. 14(b) shows an arrangement in whichan optical focusing element is incorporated in the LED.

FIGS. 15(a) to 15(c) are side views showing a schematic arrangement ofthe light guide body in still another embodiment of the presentinvention. FIG. 15(a) shows an arrangement in which the reflection meansis provided outside the scattering dots. FIG. 15(b) shows an arrangementin which the reflection dots are formed between the second light guidelayer and a third light guide layer. FIG. 15(c) shows an arrangement inwhich light spreading agents are dispersed in the second light guidelayer.

FIG. 16 is a side view showing a schematic arrangement of a light guideplate and a lighting apparatus in still another embodiment of thepresent invention.

FIG. 17 is a side view showing a schematic arrangement of a light guideplate and a lighting apparatus in still another embodiment of thepresent invention.

FIG. 18 is a side view showing a schematic arrangement of a light guideplate and a lighting apparatus in still another embodiment of thepresent invention.

FIG. 19 is a side view showing a schematic arrangement of a light guideplate and a lighting apparatus in still another embodiment of thepresent invention.

FIGS. 20(a) to 20(c) are side views showing a schematic arrangement of alighting apparatus in still another embodiment of the present invention.FIG. 20(a) shows an arrangement in which a prism is provided near thelight source. FIG. 20(b) shows an arrangement in which a curved mirroris provided near the light source. FIG. 20(c) shows an arrangement inwhich the light guide surface of the first light guide layer isinclined.

FIG. 21 is a side view showing a schematic arrangement of a lightingapparatus in still another embodiment of the present invention.

FIGS. 22(a) to 22(d) are side views showing a schematic arrangement of aflat light source apparatus of the present invention. FIG. 22(a) showsan arrangement in which two lighting apparatuses are placed side byside, each of which has a reflection section on each end surface. FIG.22(b) shows an arrangement in which two lighting apparatuses are placedside by side, each of which has an elbowed reflection section. FIG.22(c) shows an arrangement in which two lighting apparatuses are placedside by side, each of which has an inclined reflection section. FIG.22(d) shows an arrangement in which two lighting apparatuses are placedside by side, each of which has a sawtooth reflection section.

FIG. 23 is a perspective view showing a schematic arrangement of aconventional light guide plate and lighting apparatus.

FIG. 24 is a side view showing a schematic arrangement of theconventional light guide plate and lighting apparatus.

FIG. 25 is a side view showing a schematic arrangement of a conventionallight guide plate and lighting apparatus.

BEST MODE FOR CARRYING OUT THE INVENTION

The following further explains the present invention with someEmbodiments and Comparative Examples, however the present invention isnot limited to those.

Embodiment 1

The following explains Embodiment 1 of the present invention inreference to the figures. A light guide plate of the present embodimentincludes (i) the first light guide layer made of a material having arefractive index n1, the first light guide layer receiving light from alight source which is distributed in a certain range of angles withrespect to the light guide plate, and (ii) a scattering light guidelayer which emits, as scattering light, the light having been incidenton the first light guide layer. The first light guide layer and thescattering light guide layer are stacked perpendicularly to thedirection of light propagation in a first light guide layer. Moreover,the light guide plate of the present embodiment is so structured that(i) the scattering light guide layer includes at least (a) a secondlight guide layer adjacent to the first light guide layer and made of amaterial having a refractive index n2 lower than the refractive index n1and (b) a scattering layer for scattering the light propagating in thesecond light guide layer, and (ii) a reflection means is provided on asurface of the first light guide layer, the surface opposite to thelight guide surface on which the light is incident, the reflection meansserving to irradiate the scattering light guide layer with the lighthaving propagated in the first light guide layer. Note that, the lightpropagation direction in the first light guide layer here denotes not adirection of local light propagation but the light propagation in theentire first light guide layer. That is, the direction of lightpropagating in the first light guide layer denotes the way from thelight guide surface to the reflection means. In other words, the lightis incident in a direction orthogonal to the direction toward which thefirst light guide layer and the second light guide layer are stacked.Moreover, the light distributed in the certain range of angles denoteslight irradiation in which light incident on the light guide surfacepropagates to the reflection means in the first light guide layer whilerepeating total reflection, and the light having -been reflected by thereflection means is incident on the second light guide layer. Note that,the light guide surface is a surface for receiving light from, forexample, a light source provided outside the first light guide layer.

FIG. 1 is a side view showing a schematic arrangement of a lightingapparatus 107 equipped with a light guide plate 100 of the presentembodiment. The light guide plate 100 of the present embodimentincludes, as basic members, a first light guide body (first light guidelayer) 101, a reflection section (reflection means) 102, a second lightguide body (second light guide layer) 103, and reflection dots(scattering layers) 104. The second light guide body 103 and thereflection dots 104 constitute a scattering light guide layer.

The first light guide body 101 is formed by a material having arefractive index n1. The second light guide body 103 is formed by amaterial having a refractive index n2 lower than the refractive indexn1. In the present embodiment, the first light guide body 101 isrealized by a 6 mm thick acrylic plate (SUMIPEX, produced by SumitomoChemical Co., Ltd.) whose refractive index n1 is set to 1.49.

Moreover, the second light guide body 103 is realized by an opticalwaveguide forming resin (produced by NTT-AT) having a refractive indexof 1.43 lower than that of the first light guide body 101. The opticalwaveguide forming resin is an ultraviolet curing resin whose viscosityand refractive index can be adjusted to desired values. Fabrication ofthe second light guide body 103 may be performed, for example, through amethod taking the steps of: dropping the optical waveguide forming resinon the first light guide body 101; and uniformizing its thickness byspin coating. The thickness of the second light guide body 103 is notespecially limited as long as it ensures guiding of the light havingbeen reflected by the reflection section 102 to the reflection dots 104.In the present embodiment, the thickness of the second light guide body103 is adjusted to substantially 0.5 mm by adjusting (i) viscosity ofthe material constituting the second light guide body 103 and (ii) therotation rate of spin coating. By exposing the optical waveguide formingresin to ultraviolet light, having a peak at 385 nm, at an intensity of10 mW/cm² for 10 minutes, the second light guide body 103 can be formedwith a desired refractive index. Note that, fabrication of the secondlight guide body 103 is not limited to this method. Each of the firstlight guide body 101 and the second light guide body 103 is tabular andhas a uniform thickness.

The light guide plate 100 of the present embodiment is so structuredthat (i) the first light guide body 101 and the second light guide body103 are optically connected with each other and (ii) the reflection dots104 for scattering light are provided on a surface of the second lightguide body 103, the surface opposite to the surface in contact with thefirst light guide body 101. Moreover, the elbowed reflection section 102is provided on a side surface (end surface) of the first light guidebody 101, and appears to be inclined when viewed from a cross section(side surface) of the light guide plate 100. This side surface is oneorthogonal to the surface of the first light guide body 101 in contactwith the second light guide body 103. The light guide plate 100 thusarranged, a cylindrical lens 105 (light focusing optical element), and alight source unit 106 which is an LED (Light Emitting Diode) constitutethe lighting apparatus 107 of the present embodiment. Moreover, thelight source unit 106 and the cylindrical lens 105 are provided on aside of a surface of the first light guide body 101, the surfaceopposite to the surface on which the reflection section 102 is provided.Note that, in the present embodiment, the light source unit 106 and thecylindrical lens 105 which is the light focusing optical elementconstitute a light source.

Note that, in FIG. 1, relative sizes of the components are exaggeratedfor better understanding, those are not the actual sizes.

FIG. 2 is a perspective view of the lighting apparatus 107 shown inFIG. 1. The light source unit 106 is constituted of a plurality of LEDs.In the present embodiment, as shown in FIG. 1, the light source unit 106in the lighting apparatus 107 includes three types of LEDs, that is, redLEDs 106 r, green LEDs 106 g, and blue LEDs 106 b. Moreover, for ease ofexplanation, the reflection dots 104 are not shown in FIG. 2.

Light emitted from the light source unit 106 has, for example, lightdistribution shown in FIG. 3. The light distribution, which denotestraveling direction and intensity of light, is shown by a polarcoordinate. A distance from an original point 0 indicates the intensityof light, and the inclination indicates an angle with respect to adirection of a center of an LED. In the present embodiment, the lighthaving emitted from one LED distributes in a range of substantially ±45degrees with respect to the direction of the center of the LED.Moreover, the intensity of this light distribution is substantially thesame in all directions. In the following explanation, a distribution oflight in a specific range is regarded as a light distribution angle(irradiation angle).

FIG. 4 shows a distribution of the light having been emitted from thelight source unit 106 and passed through the cylindrical lens 105. Sincethe effect of lens cannot be obtained in a direction of long side of thecylindrical lens 105 shown in FIG. 2, in other words, in a direction inwhich the cylindrical lens 105 extends (hereinafter referred to as“direction horizontal to the light guide surface”), the lightdistribution shown in FIG. 4(a) is substantially the same as that shownin FIG. 3. On the other hand, since the effect of lens can be obtainedin the direction along the short side, which is orthogonal to the longside of the cylindrical lens 105, in other words, in the directiontowards the reflection section 102 from the cylindrical lens 105, instill other words, in the direction of the way connecting the lightguide surface and the reflection section 102 (hereinafter referred to as“direction perpendicular to the light guide surface”), the lightdistribution is changed as shown in FIG. 4(b). In this case, the lightdistributes in a narrower range of angles than that of the light emittedfrom the light source unit 106. In the present embodiment, in thedirection of the way connecting the light guide surface and thereflection section 102, the light distributes in a range ofsubstantially ±20 degrees with respect to the direction of the center ofthe LED. More specifically, the cylindrical lens 105 is so designed thatthe light distribution angle is in a range of ±20 degrees. The LED isnot a point light source technically, as it emits light from a chiphaving a certain square measure; therefore there generally are somedifficulties in producing completely parallel light from LEDs. Moreover,there are variations depending on the type of light source or lot-to-lotvariations, which makes it difficult to completely control thedistribution of light. However, as described in the present embodiment,it is easy to adjust the light distribution angle within a relativelywide range of angles, for example, about ±20 degrees. Moreover, withregard to the distribution of light having passed through thecylindrical lens 105, comparatively free control is possible by changinga focus position of the cylindrical lens 105. Moreover, the cylindricallens 105 may instead be the light focusing optical element having thesame effect, such as a convex lens with a light-focusing effect and highlight transmittance. However, if attempting to focus all of light rayshaving been emitted from the LED regardless to different directions, itis necessary to provide an enough distance for mixing the light emittedfrom the LED. Therefore, if it is more desirable to mix the light withina short distance, an anisotropic lens, such as the cylindrical lens,should be used. Necessity of the light focusing optical element, such asthe cylindrical lens, depends on the type of the light source. It is notnecessary to provide the light focusing optical element in the casewhere the original light source has a function of focusing light, inother words, the light source is comparatively close to the parallellight.

Moreover, an antireflection treatment is carried out to the surface ofthe cylindrical lens 105 used in the present embodiment. Such treatmentto the optical lens further improves the transmittance of light.

The light whose distribution has been controlled by the cylindrical lens105 is incident on the first light guide body 101. The distribution ofthe light in this case is shown in FIG. 5 by using an orthogonalcoordinate. A horizontal axis of the light distribution schematicallyshows an angle in a direction perpendicular to the light guide surface,and a vertical axis schematically shows an intensity of light. Notethat, in the following explanation, an intensity distribution of thelight distributed in the certain range of angles is not especiallylimited. For convenience, an intensity of the light of the vertical axisis constant regardless of the intensity.

FIG. 5(a) shows the light distributed in the light distribution angle of±20 degree as focused by the cylindrical lens 105. The lightdistribution of the present embodiment is shown in FIGS. 5(a) and 5(b),and FIG. 6(a) schematically shows the angular relation of these lights200 and 201. Note that, in the following explanation of FIGS. 6, theincident axis of light is defined as 0 degrees, the angle of the lightinclined to the second light guide body 103 when viewed from the axis isdefined as a minus angle, and the angle of the light oppositely inclinedis defined as a plus angle. This remains unchanged regardless of thetraveling direction (outward or homeward) of light. Note that, theincident axis of light faces to a direction perpendicular to the lightguide surface of the present embodiment, that is, to a directionparallel to the stacking surface of the light guide body. Note that, thestacking surface and the light guide surface are orthogonal to eachother in the present embodiment.

When the light having been focused by the cylindrical lens 105 in thelight distribution range of ±20 degrees is incident on the first lightguide body 101, the light distributes in a light distribution angle ofsubstantially ±13.3 degrees. More specifically, the light having beenincident on the first light guide body 101 distributes in a range fromsubstantially −13.3 degrees to substantially +13.3 degrees when viewedfrom the light guide surface. A phenomenon of changing the lightdistribution angle is caused by an effect of light refraction, whichoccurred when the light is incident from the air having the refractiveindex of substantially 1 on the first light guide body 101 having therefractive index of 1.49. The light is shown by arrows of lights 202 and203 in FIG. 6(a).

As shown in FIGS. 6(a) and 6(b), the first light guide body 101 has twointerfaces: an interface 108, the interface of the air, and an interface109, the interface of the second light guide body 103. According to thecondition of total reflection, incident light undergoes the totalreflection at the interface of the first light guide body 101, havingthe refractive index n1 of 1.49, and the air (refractive index;substantially 1), when the incident angle with respect to the normalline of the interface is larger than substantially 42.2 degrees. Thatis, the light having been incident on the interface in a range of ±47.8degrees undergoes the total reflection (see FIG. 6(c)). As shown in FIG.5(b), the light having been incident on the first light guide body 101is distributed in a range of light distribution angles substantially±13.3 degrees. Because this satisfies the condition of the totalreflection, the light is not emitted to the air. The light is shown bylight 204 in FIG. 6(a). That is, in the present embodiment, the lightincident on the first light guide body 101 has a specific lightdistribution angle so that the light undergoes the total reflection asit is incident onto the interface 109 of the first light guide body 101and the second light guide body 103.

Moreover, the condition of the total reflection at the interface 109 ofthe second light guide body 103 is determined by the refractive indicesof two light guide bodies. The incident light undergoes the totalreflection when the angle with respect to the normal line of theinterface is larger than substantially 73.7 degrees. That is, the lightincident on the interface in a range of substantially ±16.3 degreesundergoes the total reflection (see FIG. 6(d)). As described above, thelight being incident on the first light guide body 101 is distributed ina range of light distribution angles substantially ±13.3 degrees asshown in FIG. 5(b). As in the interface 108 of the air, the lightsatisfies the condition of the total reflection. Therefore, the lightpropagating in the first light guide body 101 is not emitted to thesecond light guide body 103 at the interface 109 of the second lightguide body 103. This light is shown by light 205 in FIG. 6(a). That is,in the present embodiment, in addition to the above condition, the lightincident on the first light guide body 101 has a specific lightdistribution angle so that (i) the light is not directly emitted fromthe interface 108 of the first light guide body 191, in other words,(ii) the light incident on the interface 108 of the first light guidebody 101 and the outside undergoes the total reflection.

That is, all the light beams emitted from the light source andpropagating in the first light guide body 101 proceeds, while repeatingthe total reflection, to a surface opposite to the light guide surface,the surface on which the reflection section 102 is provided.

The reflection section 102 can be created by, for example, (i) cutting aside surface of the first light guide body 101 in the shape of mountainby using a laser cutter, (ii) polishing the side surface having beingcut, and (iii) forming an aluminum film on the side surface. Instead ofthe aluminum film, any material having light reflection property can beused. However, because efficiency of light utilization is greatlyaffected by the light reflectance of the reflection surface, it isdesirable to choose a reflection film having as high reflectance aspossible. The reflection section 102 may be provided via an air layer,this arrangement is however not desirable as it causes the light lossbecause of interface reflection with the air. On this account, in orderto improve the efficiency of light utilization, it is most effective toform a dielectric multilayer film on the side surface of the first lightguide body 101.

In the present embodiment, an oblique angle of the reflection section102 is set to substantially 15 degrees. In other words, as shown in FIG.1, the reflection section 102 is so formed as to be inclined atsubstantially 15 degrees with respect to the light guide surface of thefirst light guide body 101. More specifically, the reflection section102 used in the present embodiment is so formed as to be substantiallyelbowed when viewed from the surface (hereinafter referred to ascross-sectional surface) perpendicular to the long side where theplurality of LEDs are provided. Moreover, the reflection section 102appears to be the shape of depression when viewed from a direction oflight illumination. That is, the cross-sectional surface is parallel tothe stacking direction of the first light guide body 101 and the secondlight guide body 103, and is perpendicular to the light guide surface.

Because the reflection section 102 is so placed as to be inclined at 15degrees with respect to the light guide surface, the light having beenincident on the reflection section 102 changes its angle by 30 degreesby reflection. As a result, as shown in FIG. 5(c), the light having beenreflected by the reflection section 102 distributes (i) in a range fromsubstantially 16.7 degrees to substantially 43.3 degrees with respectthe light guide surface and (ii) in a range from substantially −16.7degrees to substantially −43.3 degrees with respect the light guidesurface. FIGS. 6(a) and 6(b) show four typical angles of light:substantially 16.7 degrees; substantially 43.3 degrees; substantially−16.7 degrees; and substantially −43.3 degrees. The light ofsubstantially 16.7 degrees is shown by light 206 in FIG. 6(b), the lightof substantially 43.3 degrees is shown by light 207 in FIG. 6(a), thelight of substantially −16.7 degrees is shown by light 208 in FIG. 6(b),and the light of substantially −43.3 degrees is shown by light 209 inFIG. 6(a).

Then, the light having been reflected by the reflection section 102proceeds to the light guide surface, and is incident on the interfaces108 and 109. Here, according to the above-described condition of thetotal reflection, the light having been incident on the interface 108 ina range of substantially ±47.8 degrees undergoes the total reflection atthe interface 108 of the air (outside). Therefore, because the lightdistribution angle of the light having been reflected by the reflectionsection 102 falls (i) in a range from substantially 16.7 degrees tosubstantially 43.3 degrees or (ii) in a range from substantially −16.7degrees to substantially −43.3 degrees, the light having been reflectedundergoes the total reflection. This is shown by light 210 in FIG. 6(b)and light 211 in FIG. 6(a).

Meanwhile, according to the condition of the total reflection, the lighthaving been incident on the interface 109 of the second light guide body103 in a range of substantially ±16.1 degrees with respect to theinterface 109 undergoes the total reflection at the interface 109.However, because the light distribution angle of the light having beenreflected by the reflection section 102 falls (i) in a range fromsubstantially 16.7 degrees to substantially 43.3 degrees or (ii) in arange from substantially −16.7 degrees to substantially −43.3 degrees,this light does not undergo the total reflection but enters into thesecond light guide body 103. Here, for example, the lights having thelight distribution angles of substantially −16.7 degrees andsubstantially −43.3 degrees are changed by the effect of refraction intothe lights having the light distribution angles of substantially −3.6degrees and substantially −40.7 degrees, respectively. These lights areshown by light 212 in FIG. 6(b) and light 213 in FIG. 6(a). That is, thelight distribution angle of the light having been reflected by thereflection section 102 and incident on the second light guide body 103falls in a range from substantially −3.6 degrees to substantially −40.7degrees.

According to the condition of the total reflection, the light having anangle larger than substantially 44.4 degrees with respect to the normalline of an interface of the second light guide body 103 and the air(outside) undergoes the total reflection at the interface. That is,total reflection occurs if the light has an angle in a range from largerthan 0 degrees to substantially ±45.6 degrees with respect to theinterface. Because the light propagating (proceeding) in the secondlight guide body 103 has the light distribution angle in a range fromsubstantially −3.6 degrees to substantially −43.3 degrees, the lightundergoes the total reflection at the interface of the second lightguide body and the outside before returning to the first light guidebody 101. Then, the light having undergone the total reflection at theinterface, that is, the light having been returned to the first lightguide body 101 refracts again, and results in the light having the lightdistribution angle in a range from substantially 16.7 degrees tosubstantially 43.3 degrees, as shown by the light 206 in FIG. 6(b) andthe light 207 in FIG. 6(a).

Note that, in the above explanation, (i) the interface 108 of the firstlight guide body 101 and the outside, (ii) the interface 109 of thefirst light guide body 101 and the second light guide body 103, and(iii) the interface of the second light guide body 103 and the outsideare parallel to each other and are orthogonal to the light guidesurface.

To sum up, in the present embodiment, the light having been incident onthe first light guide body 101 in the range of angles ±20 degreesrepeats the total reflection in the first light guide body 101 as itproceeds to the reflection section 102. Then, the light is reflected bythe reflection section 102 where its angle is changed. The reflectionlight of the reflection section 102 undergoes the total reflection atthe interface 108 of the first light guide body 101 and the outside, butis refracted by the interface 109 of the first light guide body 101 andthe second light guide body 103 and is incident on the second lightguide body 103. Moreover, the light having been incident on the secondlight guide body 103 undergoes the total reflection at the interface ofthe second light guide body 103 and the outside. That is, the reflectionlight of the reflection section 102 repeats the total reflection between(i) the interface 108 of the first light guide body 101 and the outsideand (ii) the interface of the second light guide body 103 and theoutside.

Incidentally, in the present embodiment, as shown in FIG. 1, thereflection dots 104 are formed on a surface of the second light guidebody 103, that is, on the interface of the second light guide body 103and the outside. Therefore, the light having been refracted by theinterface 109 and incident on the second light guide body 103 isincident on the reflection dots 104. Then, the light having beenincident on the reflection dots 104 is scattered/reflected by thereflection dots 104. At this point, the traveling way of the light isdirected perpendicular to the interface of the second light guide body103 and the outside in a direction of the first light guide body 101when viewed from the second light guide body 103. That is, the light isemitted outward at the interface 108 of the first light guide body 101and the air.

Note that, light not having been incident on the reflection dots 104,that is, the light not having scattered/reflected keeps on traveling bythe total reflection, but a part thereof is incident on other reflectiondots 104 and the same results are repeated. Before the light eventuallyreturns to the end surface (light guide surface) of the light incidentside, substantially all the light beams having been incident on thelight guide surface of the first light guide body 101 is emitted fromthe light guide plate 100. On this account, by appropriately designingthe disposition of the reflection dots 104, it becomes possible toobtain the light guide plate 100 and the lighting apparatus 107, both ofwhich realize the high efficiency of light utilization. Needless to say,it is easy to form a uniform light emitting surface by appropriatelydesigning the reflection dots 104. Optimization of the reflection dots104 is achieved in many of existing products.

In some cases, the scattering by the reflection dots 104 may generatestray light, which is emitted from the second light guide surface 103 tothe air, that is, toward the direction opposite to the direction towardwhich most light is emitted. In this case, efficiency of light emissioncan be further improved by, for example, providing a reflection plate(not shown) outside the second light guide body 103, that is, providingthe reflection plate on the side which is opposite, when viewed from thereflection dots 104, to the side where the second light guide body 103is formed.

As described, in the above arrangement, a part of the incident light onthe second light guide surface 103 is scattered/reflected by thereflection dots 104. Moreover, the light having been incident on thelight guide surface of the first light guide body 101 repeats the totalreflection in the first light guide body 101 until the light reaches thereflection section 102, and therefore the light is not incident on thereflection dots 104. At this time, the colors of LEDs are mixed. Here,the light is not emitted to the outside from the first light guide body101, and therefore is invisible. Further, color unevenness and luminancenonuniformity are substantially disappeared before the light reaches thereflection section 102. When this light is emitted outside the lightguide plate 100 by the reflection dots 104, the light becomes visiblefor the first time. On this account, a planar light source with almostno visible luminance nonuniformity or color unevenness is obtained.

Although the lighting apparatus 107 arranged as above uses LEDs whichare red, green, and blue point light sources, the lighting apparatus 107serves as an even planar light source in which the colors are completelymixed, and no color unevenness or luminance nonuniformity of the LEDs isseen.

Moreover, when the lighting apparatus 107 of the present embodiment isapplied to, for example, an illumination table lamp, it is possible toobtain uniform emission of white light. This illumination table lamp isalso capable of producing any desired white light by individuallychanging light quantity of red, blue, and green LEDs, without causingluminance nonuniformity or color unevenness. In addition to theapplication to the illumination table lamp, the lighting apparatus 107may be applied for, for example, an illumination lamp attached to aceiling or a wall. Moreover, the lighting apparatus 107 of the presentembodiment can emit light of other colors than white by changingsettings of the light source unit 106 which is the point light source.Therefore, the lighting apparatus 107 is suitable not only for anillumination lamp with improved brightness but also for the illuminationlamp for creating a good atmosphere. More specifically, by changing theratio of light sources (LEDs) of three primary colors: red, green, andblue of the light source unit 106, it becomes possible to emit light ofvarious colors.

Moreover, in the light guide plate 100 of the present embodiment, thefirst light guide body 101 serves to both mix the colors and provide apractical planar light source, simultaneously.

With this structure, it becomes possible to reduce the thickness of theentire light guide plate as compared with an arrangement in which thecolor mixing and the planar light source producing are carried out byseparate light guide plates.

In the light guide plate 100 of the present embodiment, the second lightguide body 103 is only required to refract the light from the firstlight guide body 101; therefore, even when the thickness of the secondlight guide body 103 is significantly reduced, a planar light source canstill be realized. On this account, it is possible to reduce thethickness of the entire light guide plate as compared with conventionalarrangements.

Moreover, the first light guide body 101 is only required to have anuniform thickness, and therefore the structure of the light guide platecan be simplified compared to the conventional arrangement in which thecolor mixing and the planar light source producing are carried out by asingle light guide plate. Moreover, since the arrangement of the lightguide plate is further simplified in the present embodiment than theconventional ones, it becomes possible to mass produce the light guideplates without causing variation in planar luminance distribution.

Moreover, it is preferable that the light source of the presentembodiment be either (i) the point light sources of a plurality ofcolors or (ii) the liner light sources of a plurality of colors. Whenthe plurality of point light sources and/or liner light sourcesrespectively emit different monochromatic lights, it becomes possible toobtain the planar light source with satisfactory color reproducibility.

In the light guide plate 100 of the present embodiment, the refractiveindices of the first light guide body 101 and the second light guidebody 103, the angle of the reflection section 102 with respect to thelight guide surface, and the range of angles (light distribution angles)of incident light are specified so that (i) the light having beenincident on the first light guide body 101 proceeds, while undergoingthe total reflection, in the first light guide body 101 until the lightis reflected by the reflection section 102, (ii) the light having beenreflected by the reflection section 102 is refracted by the interface ofthe first light guide body 101 and the second light guide body 103before being incident on the reflection dots 104, thereafter (iii) thelight becomes the scattering light.

More specifically, (i) materials of the first light guide body 101 arechosen so that the refractive index n1 becomes 1.49, and the refractiveindex n2 of the second light guide body 103 becomes 1.43, (ii) thereflection section 102 is so placed as to be inclined by 15 degrees withrespect to the light guide surface, and (iii) the light is incident onthe first light guide body 101 with a light distribution angle of 13.3degrees. With this arrangement, the light guide plate produces furtheruniform planar light source.

Moreover, fabrication of the light guide plate 100 is easy, as each ofthe first light guide body 101 and second light guide body 103 of thepresent embodiment has a uniform thickness and tabular.

Embodiment 2

The following explains another embodiment of the present invention inreference to FIG. 7. Note that, for ease of explanation, the samereference numerals are used for the members having the same functions asthe members used in Embodiment 1, and the explanations thereof areomitted.

FIG. 7 is a side view showing a schematic arrangement of a light guidebody 120 and a lighting apparatus 127 of the present embodiment. InEmbodiment 2, the light guide plate 120 includes, as basic members, thefirst light guide body 101 having the refractive index n1, the secondlight guide body 103 having the refractive index n2 lower than therefractive index n1, a third light guide body 110 having a refractiveindex n3 higher than the refractive index n2, the reflection section102, and the reflection dots 104. The second light guide body 103 isformed between the first light guide body 101 and the third light guidebody 110, and those light guide bodies are optically connected with eachother. Moreover, the reflection dots 104 are formed on a surface of thethird light guide body 103, the surface opposite to a surface in contactwith the second light guide body 103. Note that, in the presentembodiment, the second light guide body 103, the third light guide body110, and the reflection dots 104 constitute a spreading light guidelayer. Further, the reflection section 102 is provided on one of the endsurfaces of the first light guide body 101, and is inclined with respectto the light guide surface. More specifically, the reflection section102 is provided on a surface (side) opposite to the light guide surfaceof the first light guide body 101.

In addition to the light guide plate 120 constituted of the basicmembers above, the lighting apparatus 127 further includes thecylindrical lens 105 which is the light focusing optical element, andthe light source unit 106 which is the light source constitute. As withEmbodiment 1, the light source unit 106 in Embodiment 2 is constitutedof a plurality of LEDs.

Note that, in FIG. 7, relative sizes of the components are exaggeratedfor better understanding, those are not the actual sizes.

In Embodiment 2, the refractive index n1 of the first light guide body101 is set to 1.49, the refractive index n2 of the second light guidebody 103 is set to 1.43, and the refractive index n3 of the third lightguide body 110 is set to 1.49 which is the same as the refractive indexn1. More specifically, as in Embodiment 1, the first light guide body101 is made of a 6 mm thick acrylic plate. The third light guide body110 is made of a 2 mm thick acrylic plate, which is the same material asthat of the first light guide body 101. The second light guide body 103is made of an adhesive dedicatedly used for optical component assembly(produced by NTT-AT). The adhesive for optical component assembly, whichis curable by being exposed to ultraviolet light, is applied into aspace between the components to be bonded together. In Embodiment 2, thesecond light guide body 103 is formed in the following manner. First,the adhesive for optical component assembly is dropped onto the firstlight guide body 101, the third light guide body 110 is put on it, andpressure is given so that the adhesive for optical component assemblyhas a uniform thickness. Then, by exposing this assembly to ultravioletlight, having a peak at 385 nm, at an intensity of 10 mW/cm² for 15minutes, the adhesive for optical component assembly is completelycured. In this way, the second light guide body 103 is formed. Here, thethickness of the second light guide body 103 is set to substantially 50μm, but it can be arbitrarily changed within a range greater than thewavelength of visible light. However, excessive reduction in thicknessof the second light guide body 103 may result in insufficient adhesivestrength. Therefore, the second light guide body 103 needs to have athickness of at least substantially several micrometers. Note that,because the second light guide body 103 is sandwiched between the firstlight guide body 101 and the third light guide body 110, it is possibleto reduce the thickness as compared with the conventional ones, meaningthat the second light guide body 103 can be formed with a small amountof adhesive for optical component assembly, thereby reducing cost.

In Embodiment 2, the basic operation theory is substantially identicalto that of Embodiment 1; therefore, the following explanation is madeonly to clarify the difference therebetween. The light from the lightsource unit 106 is focused by the cylindrical lens 105 in a range of thelight distribution angles substantially ±20 degrees. The lightdistribution angle is not especially limited, however a narrower rangeis more preferable. The light having been focused by the cylindricallens 105 is incident on the light guide surface (surface opposite to thesurface on which the reflection section 102 is formed) of the firstlight guide body 101, and repeats the total reflection by inner surfacesof the first light guide body 101 until it reaches the reflectionsection 102, thus ensuring the effect explained in Embodiment 1. As withEmbodiment 1, the reflection section 102 is so provided as to have anoblique angle of 15 degrees with respect to the light guide surface.That is, the light having traveled in the first light guide body 101changes its angle by 30 degrees as it reaches the reflection section 102before proceeding to the second light guide body 103. Whereas thereflection section 102 is elbowed in Embodiment 1, the reflectionsection 102 in Embodiment 2 is inclined toward the second light guidebody 103 when viewed from the cross-sectional surface. This arrangementis however optically the same as that in Embodiment 1, and is totallyallowable. Moreover, in terms of assembly, the reflection section 102 inEmbodiment 2 can be fabricated with less number of processing steps,particularly for cutting steps or disposing steps of the member forreflection, such as an aluminum film. Moreover, even when aninexpertly-designed reflection section 102 causes light leakage from thereflection surface, the defect would not be significant.

As one of the notable differences from Embodiment 1, Embodiment 2further includes the third light guide body 110 outside the second lightguide body 103, that is, on a surface of the second light guide body103, the surface opposite to the surface on which the first light guidebody 101 is provided. In contrast to Embodiment 1 in which the lighthaving traveled in the second light guide body 103 undergoes the totalreflection at the interface of the second light guide body 103 and theair, the present embodiment causes the light to refract again at thesecond light guide body 103, which is in contact with the third lightguide body 110. Because the progress of light in the case above is thesame as that of the light from the second light guide body 103 to thefirst light guide body 101, it can be easily estimated by analogy whenthe refractive indices of the first light guide body 101 and the thirdlight guide body 110 are identical. That is, the total reflection doesnot occur in the light proceeds from the second light guide body 103 tothe third light guide body 110, but the light undergoes the totalreflection at an interface of the third light guide body 110 and the airas it is incident on the third light guide body 110. The principle ofthis reflection is the same as that for causing the light to undergo thetotal reflection at the interface of the first light guide body 101 andthe air.

As described, the light having distributed in a range of the lightdistribution angles ±20 degrees and having been incident on the firstlight guide body 101 repeats the total reflection in the first lightguide body 101 before reaching the reflection section 102, and changesits angle by the reflection section 102. Then, the light having beenreflected by the reflection section 102 repeats the total reflection atthe interface of the first light guide body 101 and the outside whilebeing refracted by the interface of the first light guide body 101 andthe second light guide body 103, and is incident on the second lightguide body 103. The light having been incident on the second light guidebody 103 is refracted by the interface of the second light guide body103 and the third light guide body 110, and is incident on the thirdlight guide body 110.

Then, the light having been incident on the third light guide body 110is scattered/reflected by the reflection dots 104 provided on the thirdlight guide body 110, while the part thereof passes through the secondlight guide body 103 and the first light guide body 101 before beingemitted from the interface of the first light guide body 101 and theoutside (air). By optimizing the placement of the reflection dots 104,it is possible to obtain the lighting apparatus which is a uniformplanar light source. The reflection plate may be provided outside thethird light guide body 110 in order to efficiently utilize the straylight.

In the present embodiment, the third light guide body 110 is furtherformed in addition to the arrangement of Embodiment 1. This arrangementhas an advantage of being capable of further reducing the thickness ofthe second light guide body 103. In addition to this, the followingadvantages can be obtained.

In comparison of (i) the angle of light in Embodiment 1 having beenincident on the second light guide body 103 on which the reflection dots104 are provided and (ii) the angle of light in the present embodimenthaving been incident on the third light guide body 110 on which thereflection dots 104 are provided, with respect to the interface of thethird light guide body 110 and the reflection dots 104, the angle oflight in the present embodiment is closer to a right angle with respectto the interface of the reflection dots 104 than the angle of light inEmbodiment 1. That is, the light of the present embodiment is incidenton the reflection dots 104 at a steeper angle than that of the light ofEmbodiment 1. This is because, in the present embodiment, the thirdlight guide body 110 in contact with the reflection dots 104 has therefractive index higher than that of the second light guide body 103.Generally, most of the light having been incident on the reflection dots104 become regular reflection light, and the intensity of the lightbecomes a Gaussian distribution centering on the angle. On this account,the light having been incident on the reflection dots 104 (interface ofthe reflection dots 104 and the third light guide body 110 adjacent tothe reflection dots 104) at an angle close to a right angle with respectto the reflection dots 104 can be emitted to the outside (air) from thelight guide plate 100 more efficiently.

Embodiment 3

The following explains another embodiment of the present invention inreference to FIG. 8. Note that, for ease of explanation, the samereference numerals are used for the members having the same functions asthe members used in Embodiments 1 and 2, and further explanationsthereof are omitted. The present embodiment explains an exampleproviding, in addition to the above arrangement, a scattering layer, byforming depressions and projections on a surface of the scattering lightguide layer which is constituted of the second light guide body, thesurface opposite to a surface in contact with the first light guidebody.

FIG. 8 is a side view showing a schematic arrangement of a light guideplate 130 and a lighting apparatus 137 of the present embodiment. InEmbodiment 3, the light guide plate 130 includes, as basic members, thefirst light guide body 101 having the refractive index n1, the secondlight guide body 103 having the refractive index n2 lower than therefractive index n1, and the third light guide body 110 having therefractive index n3 higher than the refractive index n2, which arestacked in this order. Those light guide bodies are optically connectedwith each other.

In the light guide plate 130 of the present embodiment, a minute pattern111 (scattering layer) physically in the shape of depressions is formedon a surface of the third light guide body 110, the surface opposite toa surface in contact with the second light guide body 103. Moreover, thereflection section 102 is formed on a surface (side) of the first lightguide body 101, the surface (side) opposite to the light guide surface.The reflection section 102 is constituted of many reflection surfaces.The reflection surfaces inclined in the same direction are parallel toeach other, making the reflection section 102 in the shape of so-calleda sawtooth.

Moreover, in the light guide plate 130 of the present embodiment, thecylindrical lens (light focusing optical element) 105 is attached to thelight guide surface of the first light guide body 101. Morespecifically, the first light guide body 101 and the cylindrical lens105 are formed integrally. That is, the lighting apparatus 137 of thepresent embodiment is constituted of the light source unit 106 and thelight guide plate 130. Moreover, as with Embodiment 1, the light sourceunit 106 of the present embodiment is constituted of a plurality ofLEDs.

Note that, in FIG. 8, sizes of the components are exaggerated for betterunderstanding, those are not the actual sizes.

In the present embodiment, the first light guide body 101 is formed by amaterial having the refractive index n1 of 1.49, the second light guidebody 103 is formed by a material having the refractive index n2 of 1.43,and the third light guide body 110 is formed by a material having therefractive index n3 which is the same as the refractive index n1. Notethat, a method of stacking the first light guide body 101, the secondlight guide body 103, and the third light guide body 110 is the same asthose of Embodiment 2.

A significant difference between the present embodiment and Embodiment 2is a method of forming the reflection section 102, the cylindrical lens105, and the minute pattern 111.

Generally, molding of an acrylic resin which is a material for the lightguide body is performed by two methods: extrusion and casting. Theextrusion is a method of manufacturing the light guide body in such amanner that a lump of acrylic resin which is not completely cured ispressed, for example, between rollers, to be thinner. Advantages of theextrusion are excellent mass productivity and low cost. However, theextrusion is unsuitable for producing the light guide body other thanstandardized products. The casting is a method of manufacturing thelight guide body by pouring molten acrylic resin into a certain mold. Anadvantage of the casting is that any shape of light guide body can bemanufactured. A disadvantage of the casting is high cost.

The first light guide body 101 of the present embodiment is manufacturedby the casting. More specifically, the first light guide body 101 ismanufactured by pouring the acrylic resin into a mold, which (i) has onone end a so-called sawtooth shape so as to form one end surface of thefirst light guide body 101, that is, the surface opposite to a surfaceon which the light guide surface is formed, and (ii) has on the otherend a shape of the cylindrical lens so as to form another end surface ofthe first light guide body 101, that is, the surface on which the lightguide surface is formed. Similarly, the third light guide body 110 ismanufactured by pouring an acrylic resin material into a mold which hasa shape of the depressed minute pattern 111.

In the case of the casting in which the light guide body is manufacturedby using the mold as described above, the cost is generally high.However, in consideration of the cost of (i) the cutting process forforming the reflection section 102, (ii) installation of the cylindricallens 105, and (iii) formation of the minute pattern 111, which arerequired when manufacturing the light guide body by the extrusion, themanufacturing through casting is simpler even though the cost is almostthe same.

Moreover, the cylindrical lens 105 formed integrally has the same effectas that of the cylindrical lens 105 adhered by an optical adhesive tothe light guide surface of the first light guide body 101.

In the present embodiment, the basic operation theory is substantiallyidentical to that of Embodiment 1; therefore, the following explanationis made only to clarify the difference therebetween. The light from thelight source unit 106 is focused in the first light guide body 101 in arange of, for example, the light distribution angles substantially ±13.3degrees by the cylindrical lens 105 formed on the end surface of thefirst light guide body 101. In Embodiments 1 and 2, the lightdistributed in a range of the light distribution angles ±20 degreesbecomes the light distributed in a range of substantially the lightdistribution angles ±13.3 degrees by refraction occurred when the lightis incident on the first light guide body 101 via the air layer. In thepresent embodiment, the light do not pass through the air layer, thatis, the first light guide body 101 and the cylindrical lens 105 areformed integrally by using the same material. On this account, it isnecessary to design the shape of the cylindrical lens 105 of the presentembodiment, assuming the light distribution angle of the lightpropagating in the first light guide body 101. However, the lightdistribution angle of the light propagating in the first light guidebody 101 is not limited to the angle in the above range, and it is morepreferable that the light be focused in a narrower range. Then, thelight irradiating the first light guide body 101 repeats the totalreflection by the inner surfaces of the first light guide body 101, andreaches the reflection section 102.

As with Embodiment 1, the reflection section 102 is so formed as to beinclined at 15 degrees with respect to the light guide surface. Then,the light having propagated to the reflection section 102 changes itsangle by 30 degrees when being reflected. In Embodiment 1, thereflection section 102 is inclined in both directions, that is, thereflection section 102 is elbowed when viewed from the cross-sectionalsurface. In the present embodiment, the reflection section 102 appearsto be a sawtooth constituted of a plurality of elbowed inclinedsurfaces. Therefore, optically, as with Embodiment 1, the light havingbeen reflected by the reflection section 102 is reflected in a directionof the second light guide body 103 and in the opposite direction, whenviewed from the first light guide body 1. Moreover, as shown in FIG. 8,the projections of the reflection section 102 in the present embodimentare short. That is, the reflection section 102 is made in the form of asawtooth constituted of a plurality of elbowed inclined surfaces havingthe same oblique angle. With this configuration, it is possible toreduce a thickness of the reflection section 102, the thickness in thedirection from the light guide surface to the surface on which thereflection section 102 is formed (in the direction perpendicular to thelight guide surface). The light guide plate 130 having the reflectionsection 102 in the form of a sawtooth can be preferably applied to aliquid crystal display apparatus having a small display periphery(so-called frame), called a narrow frame which is now becoming themainstream.

A significant difference between the present embodiment and Embodiment 2is the minute pattern 111, which is formed on a surface of the thirdlight guide body 110, the surface opposite to a surface on which thesecond light guide body 103 is formed. Then, the light having beenincident on the third light guide body 110 is reflected by the minutepattern 111, and is emitted to the outside of the light guide plate 130,that is, emitted to the outside of the first light guide body 101.

The shape of the minute pattern 111 is different from that of thereflection dot 104 of Embodiment 2, but basic functions are the samewith each other. That is, a part of the light having undergone the totalreflection is emitted to the outside of the light guide plate 130.Because the direction of light emission can be freely controlled by theshape of the minute pattern 111, it is possible to increase efficiencyof light extraction. In the present embodiment, the minute pattern 111is formed on the third light guide body 110 and is projected toward thesecond light guide body 103. However, the shape of the minute pattern111 is not especially limited. For example, the projection of minutepattern 111 may be formed on the other surface of the third light guidebody 110, the surface opposite to a surface on which the second lightguide body 103 is adhered, so that the minute pattern 111 is projectedwhen viewing the third light guide body 110 from the side of the secondlight guide body 103.

Moreover, the minute pattern 111 explained above is created by formingdepressions on the third light guide body 110. However, for example, amedium, such as monomers, having a density different from the thirdlight guide body 110 may be injected into the depressions. Here, arefractive index distribution occurs due to diffusion of the medium. Asa result, the light is scattered also in this arrangement at aninterface of the third light guide body 110 and the medium. That is tosay, the minute pattern 111 can be a component having opticaldepressions and projections.

Embodiment 4

The following explains still another embodiment of the present inventionin reference to FIG. 9. Note that, for ease of explanation, the samereference numerals are used for the members having the same functions asthe members used in Embodiments 1 to 3, and further explanations thereofare omitted.

FIG. 9 is a side view showing a schematic arrangement of a light guideplate and a lighting apparatus of the present embodiment. In Embodiment4, a light guide plate 140 includes, as basic members, the first lightguide body 101 having the refractive index n1, and a plurality of thesecond light guide bodies 103 each having the refractive index n2 lowerthan the refractive index n1. Those light guide bodies are opticallyconnected with each other. Moreover, the reflection dots 104 are formedon a surface of each second light guide body 103, the surface oppositeto a surface on which the first light guide body 101 is formed. Further,the reflection section 102, which is not inclined physically, isprovided on one end surface of the first light guide body 101, that is,on a surface opposite to the light guide surface. The reflection section102 is formed by holography, and has a function of off-axis. That is, inthe present embodiment, the reflection section 102 is constituted of ahologram. By using the holography, it is possible to obtain highlyefficient reflection and give the function of off-axis. The off-axismeans an effect that an the angle of the regular reflection (reflectionangle) changes apparently. For example, when light is incident on amirror at +30 degrees with respect to the normal line of a reflectionsurface, the reflection angle becomes the same as the incident angle of30 degrees. Meanwhile, when light is incident on the hologram, whoseoff-axis is 15 degrees, at 30 degrees, the reflection angle can be 45degrees (or 15 degrees). That is, even though the hologram is flat andis parallel to the light guide surface, the hologram functions in thesame way as the mirror inclined with respect to the light guide surface.Moreover, as with Embodiment 3, the cylindrical lens 105 is integrallyformed on the light guide surface of the first light guide body 101 inthe present embodiment. Thus, by integrally forming the cylindrical lens105 and the first light guide body 101, it is possible to avoid thelight loss which is caused by reflection at the above-described twointerfaces. Further, the lighting apparatus 147 is constituted of thelight guide plate 140 having the same as above and the light source unit106 which is the light source constitute. As with Embodiment 1, thelight source unit 106 is constituted of a plurality of LEDs in thepresent embodiment.

Note that, in FIG. 9, sizes of the components are exaggerated for betterunderstanding, those are not the actual sizes.

In the present embodiment, the first light guide body 101 is formed by amaterial having the refractive index n1 of 1.49, and the second lightguide body 103 is formed by a material having the refractive index n2 of1.43. More specifically, as with Embodiment 2, the acrylic plate is usedas the first light guide body 101, and the adhesive for opticalcomponent assembly is used as the second light guide body 103.Fabrication of the reflection dots 104 is mostly performed by screenprinting. The screen printing is a method of printing, for example,materials (solution containing TiO₂, etc.) of the reflection dots 104using a screen plate having desired dot patterns. By using a masterplate having a mask pattern, it is possible to inexpensively produce alarge number of screen plates having the same pattern. Because thesecond light guide body 103 and the reflection dot 104 are formed atsubstantially the same place in the present embodiment, it is possibleto use the screen plates which are produced by the same master plate.The screen plate is much lower in price than the master plate, so thatthe cost can be reduced. Further, it is also possible to simultaneouslyapply materials of the reflection dot 104 and the second light guidebody 103, by mixing them together.

In the present embodiment, the basic operation theory is substantiallyidentical to that of Embodiment 1; therefore the following explanationis made only to clarify the difference therebetween. The light from thelight source unit 106 is focused in a range of the light distributionangles substantially ±13.3 degrees by the cylindrical lens 105 formed onthe end surface (light guide surface) of the first light guide body 101.In Embodiments 1 and 2, the light distribution angle is in a range of±20 degrees, which is different from the present embodiment. InEmbodiments 1 and 2, the light distribution in a range of ±20 degreesbecomes the light distribution in a range of substantially ±13.3 degreesdue to the refraction occurred when the light is incident on the firstlight guide body 101 via the air layer. However, in the presentembodiment, the air layer is not provided between the cylindrical lens105 and the first light guide body 101. Therefore, the cylindrical lens105 needs to be designed in light of the light distribution angle in thefirst light guide body 101. However, the light distribution angle is notespecially limited, and the narrower angle range is more preferable.Then, the light having irradiated the first light guide body 101 repeatsthe total reflection by the inner surfaces of the first light guide body101 before reaching the reflection section 102. The reflection section102 is the hologram whose off-axis is 15 degrees. Therefore, the lighthaving been guided to the reflection section 102 changes its angle by 30degrees before being incident on the second light guide body 103. Notethat, the reflection section 102 constituted of the hologram is not soprojected, that is, the thickness of the reflection section 102 in adirection from the light guide surface to the surface opposite to thelight guiding surface (in a direction perpendicular to the light guidesurface) is very thin. As described, the light guide plate 140 in whichthe reflection section 102 is made of a hologram can be preferablyapplied to a liquid crystal display apparatus having a small displayperiphery (so-called frame), called a narrow frame which is becoming themainstream.

A significant difference between the present embodiment and Embodiment 2is that the second light guide bodies 103 is provided only partially. Inother words, in the present embodiment, the second light guide bodies103 and the reflection dots 104 are provided partially on a surface ofthe first light guide body 101. The above arrangement is different fromthat in Embodiment 1, but the functions of the above arrangement is thesame as those of the arrangement in Embodiment 1. The following explainsthe reason for this theory.

The light having irradiated from the cylindrical lens 105 formed on thelight guide surface propagates to the reflection section 102 byrepeating the total reflection. Then, when the light having beenreflected by the reflection section 102 is incident on a portion wherethe second light guide body 103 is not formed, the light propagates inthe first light guide body 101 while repeating the total reflection; onthe other hand, the light having been incident on the second light guidebody 103 is guided to the reflection dot 104. That is, the second lightguide bodies 103 is only required to be provided on potions where thereflection dots 104 are formed. Thus, because the second light guidebodies 103 are formed only on potions where the reflection dots 104 areformed, the material for forming the second light guide bodies 103 canbe reduced. Therefore, the cost can be reduced. Moreover, the interfaceof the first light guide body 101 and the second light guide bodies 103is narrowed, thereby realizing further higher efficiency.

As shown in FIG. 10, a liquid crystal display apparatus (displayapparatus) of the present embodiment includes a liquid crystal panel 112which is provided at a position on which the light from the lightingapparatus 147 is incident. In other words, the display apparatus of thepresent embodiment includes the liquid crystal panel 112, the lightguide plate 140 explained above, and the light source unit 106 of threeprimary colors (R, G, and B).

In terms of the function as a light source, the LED has the followingsuperior features: (1) the luminous efficiency improves remarkably,suggesting a possibility that the LED achieves greater power reductionthan a fluorescent lamp in the future; (2) the color reproducibility ishigh because emission spectra are dense; (3) because the LED has a longlife, maintenance, such as changing the light source, is not necessary;(4) because mercury is not used, LED is more environmentally friendly;and (5) regardless of environmental temperature, the LED can beactivated at a high speed.

However, because the LED is generally the point light source and threeprimary colors are separated, there has been some difficulties in usingLED as a backlight of a display apparatus etc. since the backlight inthis application needs to be a white uniform planar light source.

As described, the display apparatus of the present embodiment uses thelight guide plate 140 explained above. More specifically, the lightguide plate 140 is constituted of a single light guide plate in which aplurality of light guide bodies are bonded. With the light guide plate140, the separate lights from the point light sources of three primarycolors are merged, and are converted into a uniform white light emittedfrom the planar light source. Therefore, by using the light guide plate140 as, for example, the backlight of the liquid crystal panel 112, itbecomes possible to realize the display apparatus having the abovesuperior features (1) to (5).

Moreover, for example, when the backlight is formed by a laser lightsource and the light guide plate of the present invention, it becomespossible to obtain further higher color reproducibility. An arbitraryLED laser may be used depending on necessary color reproducibility,power, size, and cost.

Embodiment 5

The following explains still another embodiment of the present inventionin reference to FIG. 12. Note that, for ease of explanation, the samereference numerals are used for the members having the same functions asthe members used in Embodiments 1 to 4, and further explanations thereofare omitted.

FIG. 12 is a side view showing a schematic arrangement of a light guideplate and a lighting apparatus of the present embodiment. As shown inFIG. 12, the lighting apparatus 157 is constituted of a light guideplate 150 and a fluorescent tube 113 which is the light source.

The light guide plate 150 of the present embodiment includes, as basicmembers, the first light guide body (first light guide layer) 101, thereflection section (reflection means) 102, a plurality of second lightguide bodies (second light guide layers) 103, and a plurality ofreflection dots (scattering layers) 104. The reflection dot 104 isformed on the second light guide body 103, and the second light guidebody 103 and the reflection dot 104 constitute the scattering lightguide layer.

With a combination of the light guide plate 150 and the fluorescent tube157, the lighting apparatus 157 of the present embodiment obtains thefollowing effects. The scattering property of the reflection dot changesdepending on wavelength (color) of the light. Therefore, in the case ofproducing the planar light source through a fluorescent tube edge, lampmethod of one-sided light illumination as shown in FIG. 11 by using thereflection dots, the following defect occurs. In contrast to the lightemitted from the center of the light guide plate, the order of lightintensity (higher to lower)is red, green, and blue in the light emittedfrom a side, close to the lamp, of the light guide plate, while theorder is blue, green, and red in light emitted from a side, far from thelamp, of the light guide plate. This has been causing the conventionalcolor unevenness on the surface.

In contrast, as shown in FIG. 12, in the case of combining (i) the lightguide plate 150 having an arrangement similar to that of the light guideplate 140 explained in Embodiment 4 and (ii) the fluorescent tube 113, apart of the incident light, which is the light distributed in a rangeout of the light distribution angles substantially ±16.1 degrees, entersinto the second light guide body 103 because of the refractive index,and is mostly scattered before reaching the reflection section 102.Therefore, as explained above, the side close to the fluorescent tube113 becomes blue and the side close to the reflection section 102becomes red. However, the light distributed in a range of the lightdistribution angles substantially ±16.1 degrees reaches the reflectionsection 102 without entering into the second light guide body 103. Then,the light is reflected by the reflection section 102, so that the lightis changed to the light distributed in a range of the light distributionangles substantially 13.9 degrees and substantially 46.1 degrees and ina range of the light distribution angles substantially −13.9 degrees andsubstantially −46.1 degrees. Then, after the angle is changed by thereflection section 102, the light enters into the second light guidebody 103. That is, because the reflection section 102 is provided at aposition opposite to the light guide surface, the light appears toproceed in the same way as in the case where the light sources areprovided on both sides of the first light guide body 101. On thisaccount, the color unevenness is offset by the light having been emittedfrom the light guide surface and the light having been reflected by thereflection section 102. Thus, it is possible to eliminate the colorunevenness which has been a conventional problem caused in thearrangement where the light is incident only on one side.

It should be noted that, the present invention is not limited to theforegoing light guide plate, the lighting apparatus using the lightguide plate, and the display apparatus, which have been described inEmbodiments 1 to 5. For example, it is obvious that the reflectionsection 102 explained in one embodiment can be applied to thearrangement of other embodiment.

Moreover, for example, the reflection section 102 can be modified asshown in examples in FIGS. 13(a) and 13(b). More specifically, thereflection section 102 can be curved when viewed from thecross-sectional surface, or can be projected in a direction of the lightguide surface when viewed from the cross-sectional surface. Note that,though the curve of the reflection section 102 shown in FIG. 13(a) isexaggerated, the angle of the light reflected by the reflection section102 is specified as an angle larger than a critical angle of the firstlight guide body 101 and the second light guide body 103, and smallerthan a critical angle of the second light guide body 103 and the outside(air). In other words, the reflection section 102 needs to be so setthat (i) the light having been reflected by the reflection section 102is refracted by the interface of the first light guide body 101 and thesecond light guide body 103 and the light proceeds in a direction of thesecond light guide body 103, and (ii) the light having been reflected bythe reflection section 102 undergoes the total reflection at theinterface of the first light guide body 101 and the outside (air). Onthis account, the light having been reflected by the reflection section102 is incident on the second light guide body 103, and is diffused bythe reflection dot 104. In this manner, it becomes possible to producean uniform planar light source.

Moreover, various modification is possible for the light focusingoptical element provided on a side of the light guide surface orattached to the light guide surface of the first light guide body 101.Specific examples are (i) an arrangement of using the cylindrical lens105 shown in FIG. 1, (ii) an arrangement in which the cylindrical lensand the first light guide body 101 are integrally formed as shown inFIG. 8, and (iii) an arrangement of using a convex lens 114 shown inFIG. 14(a). For example, in order to realize the foregoing arrangementin which the light having been emitted from the light source unit 106and having been distributed in a range of the distribution angles ±45degrees is focused by the convex lens 114 with a light distributionangles ±20 degrees, when the first light guide body 101 has a thicknessof 10 mm, it is necessary to set a 2 mm thick convex lens 114 having acurvature of 13 mm on a portion away from a light emitting point of theLED by 3.2 mm. Note that, the convex lens 114 may be a centrosymmetriclens, but it is more preferable to use a lens which induces anisotropyin the light irradiating the light guide surface, that is, the light isanisotropic depending on whether the light is propagating in a directionperpendicular to the light guide surface, or is propagating in adirection horizontal to the light guide surface. Further, for example,as shown in FIG. 14(b), the light source, such as the LED, may bedirectly provided without using the light focusing optical element(lens). Especially, in recent years, the LED having a light-focusingfunction has been put to practical use. With the use of such LED, thelight focusing optical element can be omitted.

Moreover, for example, there are various arrangements of lightscattering means, such as the reflection dot 104. For example, in FIG.15(a), the reflection dots 104 are formed on the surface of the secondlight guide body 103 having a low refractive index, and further,reflection plates 115 are provided between the reflection dots 104. Thisarrangement is effective to put back the stray light which has notreturned to the first light guide body 101 upon scattering/diffusion bythe reflection dots 104. The reflection plate 115 may be made of a whitesheet of foamed PET (polyethylene terephthalate).

FIG. 15(b) shows an example in which the position of the reflection dots104 is changed. In this example, the reflection dots 104 are formedinside the third light guide body 110. The reflection dots 104 may beformed on a surface of the third light guide body 110, the surface on aside of the air as in the case above, or on a surface of the third lightguide body 110, the surface on a side of the second light guide body103.

In FIG. 15(c), light diffusing materials (light scattering objects) 116are used instead of the reflection dots 104. The light diffusingmaterials 116 are dispersed in the second light guide body 103. Thelight having passed through the second light guide body 103 and havingundergone the total reflection at the interface of the second lightguide body 103 and the air is scattered by the light diffusing materials116 located in the light path, and the diffused light proceeds in adirection of the first light guide body 101. Moreover, by placing thereflection plate 115 on a surface of the second light guide body 103,the surface opposite to a surface in contact with the first light guidebody, the diffused light is emitted from the light guide plate moreefficiently. Moreover, dispersion of the light diffusing materials 116in the second light guide body 103 may be carried out by a method takingthe step of mixing the second light guide body 103 with fine particles,such as glass or plastic beads (light diffusing materials), havingrefractive index different from that of the second light guide body 103and having a diameter of substantially several micrometers. Moreover,silver fine particles (several micrometers) or hollow fine particles canbe mixed as the light diffusing materials 116.

Moreover, as shown in FIG. 16, the thickness of the first light guidebody 101 is not especially limited, and each thickness of the firstlight guide body 101 and the second light guide body 103 can bedetermined arbitrarily. Therefore, for example, the second light guidebody 103 can be thicker than the first light guide body 101 as shown inFIG. 16.

Moreover, for example, in an arrangement in which the first light guidebody 101, the second light guide body 103, and the third light guidebody 110 are stacked as shown in FIG. 17, the second light guide body103 may have the greatest thickness, which is sandwiched between thefirst light guide body 101 and the third light guide body 110 bothhaving a high refractive index.

As shown in FIG. 18, (i) positions of the light guide body (first lightguide body 101) having a high refractive index and the light guide body(second light guide body 103) having a low refractive index and (ii) adirection of light emission can be changed by scattering means(scattering layer), such as the light diffusing materials 116. In thisexample, after the light has been incident on the first light guide body101 having the high refractive index, the light having been incident isguided to the reflection section 102 while repeating the totalreflection in the first light guide body 101. Then, the light havingbeen reflected by the reflection section 102 is guided into the firstlight guide body 101 and the second light guide body 103. The lighthaving been guided to the second light guide body 103 is scattered tothe outside (air) from the second light guide body 103 by the lightdiffusing materials 116 contained in the second light guide body 103.Here, by placing the reflection plate 115 on the interface of the firstlight guide body 101 and the outside (air), the stray light can beefficiently emitted from the first light guide body 101.

Moreover, for example, as shown in FIG. 19, the second light guidebodies 103 may be provided on both sides of the first light guide body101, and the light diffusing materials 116 may be contained in eachsecond light guide body 103. Note that, instead of the second lightguide body 103 containing the light diffusing materials 116, the secondlight guide bodies 103 each having the reflection dots 104 on a surfaceopposite to a surface in contact with the first light guide body 101 canbe formed on both sides of the first light guide body 101.

As shown in FIG. 19, the cylindrical lens 105 and the light source unit106 are provided on the light guide surface of the first light guidebody 101, and the reflection section 102 is provided on a surfaceopposite to the light guide surface. In this arrangement, the lighthaving undergone the total reflection in the first light guide body 101is changed in distribution angle and is reflected by the reflectionsection 102. Then, the light having been reflected by the reflectionsection 102 proceeds between the two second light guide bodies 103. Thelight having been scattered by the light diffusing material 116 isemitted from the respective outer surfaces of the two second light guidebodies 103, that is, the light is emitted from both surfaces of thelight guide plate. By using the light guide plate thus arranged, it ispossible to easily realize, for example, a double-sided display in whichliquid crystal panels are provided on both sides of the display. Theforegoing display apparatus can be used as a display for displayinginformation on both sides of the display, such as a road traffic sign.Moreover, by adjusting distribution and density of the light diffusingmaterials 116 or the reflection dots 104, it becomes possible todifferentiate illuminance between a front surface and a back surface ofthe lighting apparatus. Moreover, the structure for emitting light fromboth sides can be created by attaching two light guide bodies ofEmbodiments 1 to 4 back-to-back, so that the both sides of the displayemit light. However, as shown in FIG. 19, by providing the second lightguide body 103 on each side of the first light guide body 101, it ispossible to further reduce the thickness and the number of components.

Moreover, as shown in FIGS. 20(a) to 20(c), there are various methods ofthe light incidence onto the first light guide body 101. None of theexamples shown in these figures include the light source unit 106 on thesame plane as that of the first light guide body 101; however, the sameeffect can be obtained. More specifically, for example, as shown in FIG.20(a), it may be arranged so that the light whose angle is changed by anoptical element 117, such as a prism, is incident on the first lightguide body 101, or that, as shown in FIG. 20(b), the light whose angleis changed by a curved reflection mirror 118 is incident on the firstlight guide body 101, or that, as shown in FIG. 20(c), the light isincident on the light guide surface which is inclined with respect tothe stacking surface of the first light guide body 101.

Moreover, a material of the second light guide body 103 having therefractive index lower than that of the first light guide body 101 usedin each embodiment can be a material which has a controllable refractiveindex and absorbs a small amount of light. In addition, a method offorming the second light guide body 103, or other members is notespecially limited. As long as the same effect can be obtained, anymaterial can be used.

Moreover, it is more preferable that the scattering layer of the presentembodiment be constituted of a light scattering object. In the abovearrangement in which the scattering layer is constituted of the lightscattering object, the scattering layer can be constituted more easilyby, for example, putting the light scattering object into the secondlight guide body 103 or the third light guide body 110 when forming thesecond light guide body 103 or the third light guide body 110. Moreover,by thus putting the light scattering object into the second light guidebody 103 so as to form the scattering layer, the second light guide body103 and the scattering layer can be formed integrally.

Next, FIG. 21 shows another modification example of the lightingapparatus of the present embodiment.

The lighting apparatus 107 shown in FIG. 21 includes the second lightguide body 103 containing the light diffusing materials 116, the lightguide plate 100, the light source unit 106, the reflection plate 115,and a mirror 119. The second light guide body 103 has two first lightguide bodies 101, the light guide surfaces of one of the first lightguide bodies 101 is opposed to the light guide surface of another lightguide body 101 with a certain gap therebetween, and the light sourceunit 106 is provided in the gap. Note that, the light source unit 106 ismade of an LED which emits light in a crosswise direction of the lightsource, so-called a side emitter type LED.

Moreover, the mirror 119 is provided between the light source unit 106and the second light guide body 103. With this arrangement, the lighthaving been slightly leaked upward the light source unit 106, that is,toward the second light guide body can be efficiently guided to thefirst light guide bodies 101. Therefore, it is possible to obtain abrighter lighting apparatus with less luminance nonuniformity and lesscolor unevenness.

The light having been incident on the first light guide bodies 101provided on both sides of the light source unit 106 is reflected by eachreflection section 102. The angle of one reflection section 102 withrespect to the light guide surface is the same as that of anotherreflection section 102 with respect to the light guide surface.

Since the above arrangement requires only one light source unit 106 fortwo light guide surfaces of the first light guide bodies 101, the spacecan be reduced.

Thus, by providing the light source unit 106 between the light guidesurfaces, it becomes possible to provide the reflection section 102 onthe outer surface of each first light guide body 101 of the lightingapparatus 107.

Next, FIG. 22(a) shows a flat light source apparatus 117 formed byplacing two lighting apparatuses 107 side by side, each having anarrangement similar to that of FIG. 21.

In the lighting apparatus 107 shown in FIG. 22(a), the reflectionsection 102 is so formed as to cover only an end surface opposite to thelight guide surface of the first light guide body 101. Meanwhile, ineach lighting apparatus 107 shown in FIG. 22(a), the reflection section102 is so formed as to cover (i) the end surface opposite to the lightguide surface of the first light guide body 101 and (ii) an end surfaceof the light guide body 103. Except for this difference, thearrangements are substantially the same with each other.

As shown in FIG. 22(a), by placing the reflection sections 102 of thelighting apparatuses 107, with no space therebetween, so as to be incontact with each other, it becomes possible to realize the flat lightsource apparatus 177 which includes two lighting apparatuses 107 placedside by side with no space therebetween. This light source apparatus 177is uniform, and has a large area.

It should be noted that the present invention is not limited to thearrangement of FIG. 22(a) in which two lighting apparatuses 107 areplaced side by side, and it may be arranged so that two or more lightingapparatuses 107 may be provided side by side. With this arrangement, itis possible to produce the flat light source apparatus which has alarger area.

According to the above arrangement, it is possible to realize the flatlight source apparatus 177 by combining a plurality of lightingapparatuses 177 having the same arrangement. Therefore, it is possibleto improve productivity in manufacturing the flat light source apparatus177.

Each of FIGS. 22(b) to 22(d) show the flat light source apparatus inaccordance with another embodiment of the present invention.

As shown in FIG. 22(b), the flat light source apparatus 167 isconstituted of (i) the lighting apparatus 107 having the elbowedreflection section as shown in FIG. 1 and (ii) the lighting apparatus107 having the reflection section to be fit in the elbowed reflectionsection with no space therebetween. That is, the reflection section 102of the flat light source apparatus 167 is formed by combining thereflection section projected and the reflection section depressed. Thus,by placing those lighting apparatuses 107 with no space therebetween, itbecomes possible to realize the flat light source apparatus 167 whichhas a large area and is capable of emitting uniform light.

FIG. 21(c) shows the flat light source apparatus 167 constituted of twolighting apparatuses 107 each having a reflection sections inclined withrespect to the light guide surface, and these reflection sections arecombined with each other.

FIG. 21(d) shows the flat light source apparatus 167 in which thereflection sections of the respective lighting apparatuses 107 shown inFIG. 8 are combined with each other.

In all of FIGS. 21(b) to 21(d), the reflection sections of therespective light guide plates of the respective lighting apparatuses 107are combined with each other, thereby realizing the flat light sourceapparatus 167 in which the light guide plates 100 have substantially nospace therebetween. With this arrangement, the light source apparatus167 is uniform and has a large area. Note that, the reflection section102 of the flat light source apparatus 167 is constituted of therespective reflection sections of the plural respective lightingapparatuses 107.

As described, it is more preferable that the light guide plate of thepresent invention include a first light guide layer on which light froma light source is incident, made of a material having a refractive indexn1; and a scattering light guide layer for emitting, as scatteringlight, light incident on the first light guide layer, the first lightguide layer and the scattering light guide layer being stacked on eachother in a direction orthogonal to a direction of light propagating inthe first light guide layer, wherein: the scattering light guide layerincludes at least (i) a second light guide layer made of a materialhaving a refractive index n2 lower than the refractive index n1,adjacent to the first light guide layer, and (ii) a scattering layer forscattering light propagating to the second light guide layer; and thefirst light guide layer includes, on a surface opposite to a light guidesurface on which the light is incident, reflection means for reflectingthe light propagating in the first light guide layer so that the lightis incident on the scattering light guide layer.

This arrangement offers the following effect: (i) substantially all thelight beams having been incident on the first light guide layer from theend surface opposite to the end surface on which the reflection means isprovided proceeds forthright, while repeating the total reflection, inthe first light guide layer until the light reaches the end surface onwhich the reflection means is provided, (ii) the light is reflected bythe end surface on which the reflection means is provided, (iii) thelight reverses its traveling direction, and (iv) the angle of the lightbeing incident on the interface is changed when the light returns in adirection of the end surface opposite to the end surface on which thereflection means is provided so that the light is incident on thescattering light guide layer.

Moreover, the thickness of the second light guide layer is determined sothat the light from the reflection means provided on the first lightguide layer is guided to the scattering layer. Therefore, it is possibleto reduce the thickness of the second light guide layer, as comparedwith a conventional arrangement of using two light guide plates.

Further, because the reflection means causes the light to proceedforward and backward in the light guide plate, it is possible to ensurereduction in thickness of the light guide plate, as compared with theconventional arrangement of using two light guide plates, reduction inweight, and improvement in efficiency of light utilization under thefavor of no light loss at a connection portion of the light guideplates. Moreover, by using the light guide layers having differentrefractive indices, it becomes possible to differentiate (i) a route ofthe light propagating to the reflection means and (ii) a route of thelight having reflected by the reflection means. Thus, the planar lightsource producing is realized.

Moreover, the light guide plate of the present invention may be soarranged that the scattering light guide layer includes two layers: (i)the second light guide layer constituted of a material having therefractive index n2 (n2<n1) and (ii) the scattering layer including thelight scattering object. With this arrangement, it is possible toseparately form the second light guide plate and the scattering layer,that is, it is possible to produce the light guide plate capable ofemitting the uniform light by using conventional arts.

Moreover, the light guide plate of the present invention may be soarranged that the scattering light guide layer is the second light guidelayer which contains the light scattering object therein and is made ofa material having the refractive index n2 (n2<n1). With thisarrangement, it becomes possible to form the second light guide layerand the light scattering object at the same time, with less number offabrication steps. In addition, it is easy to adjust the concentrationof the scattering objects, thereby easily controlling the frontscattering and the back scattering.

Moreover, the light guide plate of the present invention may be soarranged that a function of scattering light is given to the secondlight guide layer by providing projections and depressions on a surfaceof the second light guide layer, the surface being opposite to a surfacein contact with the first light guide layer. With this arrangement, itbecomes possible to form complex projections and depressions whichscatter light more efficiently than the reflection dots.

Moreover, the light guide plate of the present invention may be soarranged that the reflection means provided on the end surface (sidesurface) of the first light guide layer reflects the light, distributedin a certain range of angles with respect to the stacking surface, inthe light having propagated in the first light guide layer so that anincident angle θ (angle relative to a normal line of the stackingsurface) with respect to the scattering light guide layer is smallerthan a critical angle θc (θc=sin⁻¹(n2/n1)). With this arrangement,substantially all the light beams having propagated in the first lightguide layer is incident on the scattering light guide layer, therebyrealizing the light guide plate which utilizes the light highlyefficiently.

Moreover, the light guide body of the present invention is characterizedin that the reflection means provided on the end surface (side surface)of the first light guide layer is constituted of a hologram. Accordingto the above arrangement, each of the end surfaces of theabove-described plurality of layers has a plain configuration, therebyomitting a process of cutting or die cutting for forming the reflectionsurface. Therefore, it is possible to reduce the thickness of thereflection means. Moreover, because the light guide plate is a simplerectangular solid, it becomes possible to simplify the manufacturingprocess, thereby producing the reflection means inexpensively.

Moreover, it is more preferable that the lighting apparatus of thepresent invention include (i) the point light source or the liner lightsource, (ii) the light guide plate, and (iii) the light focusing opticalelement for focusing the light incident on the first light guide layerof the light guide plate, so that the light is focused in a certainrange of angles with respect to the stacking surface of the light guideplate. With this arrangement, the angle of the light incident on thelight guide plate from the light emitting means can be appropriatelyadjusted so that the efficiency of light utilization is maximized, andthe amount of light obtained from the surface of the light guide bodycan be increased. Moreover, even when using a light source which emitslight with an angular distribution wider than an angular distributionrequired by the light guide body, the optical element changes theangular distribution of the light from the light source, thus ensuringthe utilization of the light source. Moreover, it is possible toefficiently change the light path so that the light proceeding forwarddoes not diffuse, and the light proceeding backward diffuses.

Moreover, the lighting apparatus of the present invention may be soarranged that the light focusing optical element is the cylindricallens. With this arrangement, in the case in which the light is incidenton the light guide body from a light emitting means in which a pluralityof point light sources, such as light emitting diodes, are set in line,(i) the range of light incident angles is narrowed down in the normaldirection of a plurality of layers in the light guide body in order thatthe light is reflected at the interfaces, and (ii) the range of lightincident angles is not narrowed down in a horizontal direction of thelayers. Thus, (i) the light having been incident from the point lightsource, such as the light emitting diode, are mixed in the horizontaldirection of the layers, so that the luminance nonuniformity and thecolor unevenness are eliminated, and (ii) in the normal direction, it ispossible to prevent the light from being leaked, by exceeding thecritical angle, to the outside of the light guide plate until the lightis reflected by the reflection means provided on the opposite surface.

Moreover, the light guide plate of the present invention may be soarranged that an optical element having a function of focusing light isformed on an end surface on which the light is incident, that is, on thelight guide surface, so that the light incident on the first light guidelayer of the light guide plate from the light source is focused in acertain range of angles with respect to the stacking surface of thelight guide plate. With the this arrangement, as compared with a case offorming and placing the optical element and the light guide bodyindividually, it is possible to avoid optical property deteriorationcaused by displacement, and also possible to always obtain desiredlighting property. Further, it is possible to reduce the light loss inthe interface.

Moreover, the light guide plate of the present invention may be soarranged that the scattering light guide layer, the first light guidelayer, and another scattering light guide layer are stacked in thisorder. With this arrangement, it is possible to realize with a simplearrangement a thin and light-weighted light guide plate capable ofemitting the light from both surfaces.

Moreover, the light guide plate of the present invention may be soarranged that one surface of the scattering light guide layer serves asthe reflection surface, which surface is opposite to a surface on whichthe first light guide layer is provided. The reflection surface is soformed that the light is emitted from only one surface of the flat lightsource. With this arrangement, it becomes possible to emit the lightmore efficiently by reflecting the stray light which has not been guidedto a surface from which the light is emitted by scattering.

It is more preferable that the display apparatus of the presentinvention use the foregoing lighting apparatus. With this arrangement,even when the display apparatus uses the point light source, it ispossible to obtain a bright and desired display image with lessluminance nonuniformity and less color unevenness. Therefore, even whenthe point light sources or separate semiconductor light sources of threeprimary colors are used as the light source, the light beams therefromcan be mixed and changed into the planar light source. In this way, itbecomes possible to use the planar light source as the backlight of thedisplay panel. Thus, it is possible to realize the display apparatuswhich ensures the following advantages of the semiconductor lightsource: less power consumption, fine color reproduction, long life,mercury-free, and high-speed activation.

Moreover, for example, by combining the light guide plate of the presentinvention and red, green, and blue LEDs so as to constitute the lightingapparatus of general illumination, it is possible to constitute thelighting apparatus which reproduces colors finely without causing thecolor unevenness.

As described above, the light guide plate of the present inventionensures the following effects: the number of components are less than,for example, that of the arrangement disclosed in Non-Patent Document 1;the light guide plate is resistant to staining as it contains no prism;because the number of interfaces is small, the light loss between theprisms is small. On this account, for example, it is possible to avoidthe defect that dust enters between the prisms, which is described inthe arrangement disclosed in Non-Patent Document 1. On this account, thelight guide plate of the present invention can be inexpensivelymanufactured. Moreover, the structure seldom require positioning,thereby simplifying the manufacturing process.

Moreover, the efficiency of light utilization of the light guide platechanges depending on its thickness. More specifically, the thicker thelight guide plate is, the more easily the light can be incident on theend surface. Moreover, when the light guide plate is thick, the numberof light reflection of light, which is traveling while repeating thetotal reflection, is reduced, thereby reducing light loss. Therefore, inconsideration of only the efficiency of light utilization, it ispreferable that the light guide plate be as thick as possible. In lightof this, for example, the arrangement disclosed in Non-Patent Document 1has serious difficulties in reducing the thickness of two light guideplates to half so as to equalize the thickness of two light guide platesand the thickness of one normal light guide plate. However, in the lightguide plate of the present invention, the first light guide body 101 hassubstantially the same thickness as that of the conventional light guideplate, and the thickness of the second light guide body 3 is reduced. Inthis way, the light guide plate of the present invention hassubstantially the same thickness as that of the conventional light guideplate, while achieving the same efficiency of light utilization. Thus,the present invention ensures the sufficient effects. On this account,it is possible to reduce the thickness of the light guide plate ascompared with the arrangement disclosed in Non-Patent Document 1.

Further, for example, unlike Non-Patent Document 2, minute designing ofthe shape of the end surface (interface) is not necessary, thusmanufacture the light guide plate by a method other than casting.Therefore, it is possible to manufacture a large size light guide plate.With the advantage of easy fabrication, the light guide plate of thepresent invention can be produced at lower cost.

A light guide plate of the present invention includes a first lightguide layer on which light from a light source is incident, made of amaterial having a refractive index n1; and a scattering light guidelayer for emitting, as scattering light, light incident on the firstlight guide layer, the first light guide layer and the scattering lightguide layer being stacked on each other in a direction orthogonal to adirection of light propagating in the first light guide layer, wherein:the scattering light guide layer includes at least (i) a second lightguide layer made of a material having a refractive index n2 lower thanthe refractive index n1, adjacent to the first light guide layer, and(ii) a scattering layer for scattering light propagating to the secondlight guide layer; and the first light guide layer includes, on asurface opposite to a light guide surface on which the light isincident, reflection means for reflecting the light propagating in thefirst light guide layer so that the light is incident on the scatteringlight guide layer.

In the above arrangement, the first light guide layer and the scatteringlight guide layer are stacked with each other. Substantially all thelight beams having been incident on the light guide surface of the firstlight guide layer proceeds forthright, while repeating the totalreflection, in the first light guide layer until the light reaches thereflection means. Then, the light is reflected by the reflection means.The light having been reflected is incident on the scattering lightguide layer. More specifically, the light having been reflected by thereflection means is incident on the second light guide layer, and thenthe light is incident on the scattering layer. The light having beenincident on the scattering light guide layer (scattering layer) isemitted as the scattering light. In this case, the second light guidelayer only has to guide the light to the scattering layer, therefore,the second light guide layer can be very thin. Therefore, for example,the thickness of the light guide plate can be reduced as compared withthe conventional arrangement in which the color mixing and the planarlight source producing are carried out by two separate light guideplates. Moreover, unlike the conventional arrangement in which the colormixing and the planar light source producing are carried out by onelight guide plate, for example, it is not necessary to finely design theshape of the light guide plate. Therefore, the light guide plate can bemanufactured easily as compared with the conventional art, so that it ispossible to mass produce the light guide plates. Note that, the lightpropagation direction in the first light guide layer here denotes not adirection of local light propagation but the light propagation in theentire first light guide layer. That is, the direction of lightpropagating in the first light guide layer denotes the way from thelight guide surface to the reflection means.

Further, it is more preferable that the light guide plate of the presentinvention be so arranged that light irradiates the first light guidelayer, the light being so set that the irradiation angle is in a certainrange of angles with respect to the light guide surface of the firstlight guide layer.

The light being so set that the irradiation angle is in a certain rangemeans light being so adjusted that (i) the light having irradiated thelight guide surface propagates in the first light guide layer from thelight guide surface to the reflection means while repeating the totalreflection, and (ii) the light having been reflected by the reflectionmeans is incident on the second light guide layer. Moreover, with regardto the light being so set that the irradiation angle is in a certainrange, it is more preferable that the light having been reflected by thereflection means propagates while undergoing the total reflection at theinterface of the first light guide layer and the outside.

In the above arrangement, the light distributed in a certain range ofangles with respect to the light guide surface irradiates the firstlight guide layer. Therefore, the light having irradiated the firstlight guide layer propagates to the reflection section in the firstlight guide layer while repeating the total reflection. Then, the lighthaving been reflected by the reflection means is incident on the secondlight guide layer. The light having been incident on the second lightguide layer becomes the scattering light in the scattering layer, andthe scattering light is emitted to the outside (outside of the lightguide plate). That is, the color mixing is carried out before the lighthaving been incident on the first light guide layer reaches thereflection means. Then, only the light having been incident on thesecond light guide layer is emitted to the outside. Therefore, byirradiating the first light guide layer with the light distributed inthe certain range of angles, it becomes possible to produce furtheruniform planar light source, and also possible to emit only the whitelight to the outside.

It is more preferable that the light guide plate of the presentinvention be so arranged that the first light guide layer includes onthe light guide surface a light focusing optical element for focusinglight incident on the first light guide layer in a certain range ofangles with respect to the light guide surface.

According to this arrangement, it is possible that the light distributedin a certain range of angles can be incident on the first light guidelayer. Therefore, it becomes possible to produce further uniform planarlight source. Moreover, because the light focusing optical element isprovided at the light guide surface, it is possible to further reducethe loss of the light incident on the first light guide layer. Moreover,for example, even when using the light source which emits lightdistributed in a range exceeding the above-described certain range, itis possible to preferably produce uniform planar light source.

It is more preferable that the light guide plate of the presentinvention be so arranged that the scattering layer and the second lightguide layer are integrally formed.

In the above arrangement, the scattering layer and the second lightguide layer are formed integrally. Therefore, it is possible to simplifythe manufacturing process of the light guide plate.

It is more preferable that the light guide plate of the presentinvention be so arranged that the second light guide layer of thescattering light guide layer contains a light scattering object.

In the above arrangement, the light scattering object is contained inthe second light guide layer. Therefore, it is possible to furtherreduce the thickness of the light guide plate.

It is more preferable that the light guide plate of the presentinvention be so arranged that the scattering layer is constituted ofdepressions and projections formed on a surface of the second lightguide layer, the surface being opposite to a surface in contact with thefirst light guide layer.

In the above arrangement, the scattering layer is formed by projectionsand depressions on an outer surface (the above-described oppositesurface) of the second light guide layer. Therefore, it is possible tofrom the scattering layer more easily.

It is more preferable that the light guide plate of the presentinvention be so arranged that the reflection means is so placed as toreflect light incident thereon within a range smaller than an angleshown by sin⁻¹ (n2/n1), when viewed from a direction perpendicular to asurface on which the scattering light guide layer is formed.

In the above arrangement, substantially all the light beams havingpropagated in the first light guide layer is incident on the scatteringlight guide layer (scattering layer). Therefore, it is possible torealize the light guide plate which utilizes the light highlyefficiently.

It is more preferable that the light guide plate of the presentinvention be so arranged that the reflection means is a hologram.

With the above arrangement, it is possible to reduce the thickness ofthe reflection means because the reflection means is constituted of thehologram. Therefore, it is possible to reduce the thickness of the lightguide plate in a side surface direction (in a direction of connectingthe reflection means and the light guide surface). Therefore, forexample, it is possible to preferably apply the light guide platearranged as above to a display whose region other than a display regionis small, that is, a narrow frame display.

It is more preferable that the light guide plate of the presentinvention be so arranged that the first light guide layer furtherincludes on the surface opposite to a surface on which the scatteringlight guide layer is formed, another scattering light guide layer.

In the above arrangement, the scattering light guide layers are providedon both sides of the first light guide layer. With this, for example, itis possible to emit the light from both sides of the first light guidelayer.

It is more preferable that the light guide plate of the presentinvention be so arranged that the scattering light guide layer furtherincludes a reflection member on a surface opposite to a surface on whichthe first light guide layer is formed.

In the above arrangement, the reflection member is provide on a side ofa surface of the scattering light guide layer, the surface opposite to asurface on which the first light guide layer is formed. Therefore, forexample, even when there is the stray light in the scattering layer, itis possible to efficiently emit the light in a direction of irradiation.

In order to solve the above problems, a lighting apparatus of thepresent invention may include the light guide plate and a light sourcefor irradiating the first light guide layer of the light guide platewith light.

With the above arrangement, it becomes possible to provide the lightingapparatus which can emit the uniform planar light.

It is more preferable that the lighting apparatus of the presentinvention be so arranged that the light source is so placed that anincident angle of the light incident on the first light guide layer withrespect to the light guide surface of the first light guide layer fallsin a predetermined range.

With the above arrangement, by irradiating the first light guide layerwith the light distributed in a certain range of angles with respect tothe light guide surface, (i) the lighting apparatus can be used as theuniform planar light source and (ii) only the white light can be emittedto the outside.

It is more preferable that the lighting apparatus of the presentinvention be so arranged that the light source includes a light focusingoptical element for focusing the light incident on the first light guidelayer of the light guide plate, so that the light is focused in acertain range of angles with respect to a stacking surface of the lightguide plate.

In the above arrangement, the light source includes the light focusingoptical element. Therefore, it is possible to irradiate the light guideplate with the light distributed in a certain range of angles.Therefore, it is possible to emit further uniform planar light.

It is more preferable that the lighting apparatus of the presentinvention be so arranged that the light focusing optical element is acylindrical lens.

In the above arrangement, by using the cylindrical lens as the lightfocusing optical element it is possible to easily irradiate the lightguide plate with the light distributed in a certain range of angles.

It is more preferable that the lighting apparatus of the presentinvention be so arranged that the light guide plate includes a pluralityof the first light guide layer on the second light guide layer which areplaced so that their light guide surfaces are opposed with a certaininterval therebetween, and the light source is provided between thelight guide surfaces.

In the above arrangement, the light source is provided between the lightguide surfaces, so that the reflection means is provided on each of theouter end surfaces of the lighting apparatuses. Therefore, by combiningthe reflection means with each other, it becomes possible to place aplurality of lighting apparatuses side by side.

Moreover, in the above arrangement, one light source is provided for twofirst light guide layers. Therefore, it is possible to save space.Moreover, because a proportion of the area of light guide plate in thearea of entire lighting apparatus is increased, it becomes possible toobtain the lighting apparatus capable of emitting the uniform lighthaving less unevenness.

It is more preferable that the lighting apparatus of the presentinvention be so arranged as to include a mirror for guiding the lightfrom the light source to the first light guide layer.

With this arrangement, it is possible to efficiently guide the light tothe first light guide layer. Therefore, it becomes possible to providethe lighting apparatus capable of emitting bright light having lessluminance nonuniformity and less color unevenness.

The flat light source apparatus of the present invention is so arrangedas to include a plurality of lighting apparatuses of the presentinvention, the lighting apparatuses being placed side by side.

With this arrangement, it becomes possible to obtain the flat lightsource apparatus capable of emitting the bright light having a largearea, less luminance nonuniformity, and less color unevenness.

The flat light source apparatus of the present invention is so arrangedthat the reflection means of one of two lighting apparatuses is opposedto reflection means of another lighting apparatus.

With this arrangement, it becomes possible to easily realize the flatlight source apparatus in which no space is provided between thelighting apparatuses by combining the reflection means with each other.Therefore, it becomes possible to provide the flat light sourceapparatus capable of emitting bright light having a large area, lessluminance nonuniformity, and less color unevenness.

The display apparatus of the present invention includes the light guideplate.

With this arrangement, it becomes possible to provide the displayapparatus which is irradiated with the uniform planar light.

INDUSTRIAL APPLICABILITY

The light guide plate and the lighting apparatus equipped therewith inaccordance with the present invention are applicable to various lightingapparatuses, such as a backlight of an electric poster, an illuminationtable lamp, an illumination lamp attached to a ceiling or a wall, etc.The display apparatus in accordance with the present invention isapplicable to a liquid crystal display, the electric poster, etc.

The embodiments and concrete examples of implementation discussed in theforegoing detailed explanation serve solely to illustrate the technicaldetails of the present invention, which should not be narrowlyinterpreted within the limits of such embodiments and concrete examples,but rather may be applied in many variations within the spirit of thepresent invention, provided such variations do not exceed the scope ofthe patent claims set forth below.

1. A light guide plate comprising: a first light guide layer on whichlight from a light source is incident, made of a material having arefractive index n1; and a scattering light guide layer for emittinglight as scattering light, the first light guide layer and thescattering light guide layer being stacked on each other, wherein: thescattering light guide layer includes (i) a second light guide layermade of a material having a refractive index n2 lower than therefractive index n1, adjacent to the first light guide layer, and (ii) ascattering layer for scattering light propagating to the second lightguide layer, the first light guide layer includes, on an end surfaceopposite to a light guide surface on which the light is incident,reflection means which changes an angle of light propagating in thefirst light guide layer and reaching the end surface, so that the lightis incident on the scattering light guide layer, and the first lightguide layer causes total reflection of light, incident on the firstlight guide layer from the light source, at (i) a surface on which thescattering light guide layer is formed and (ii) a rear surface.
 2. Thelight guide plate as set forth in claim 1, wherein the first light guidelayer includes on the light guide surface a light focusing opticalelement for focusing light incident on the first light guide layer in acertain range of angles with respect to the light guide surface.
 3. Thelight guide plate as set forth in claim 1, wherein the scattering layerand the second light guide layer are integrally formed.
 4. The lightguide plate as set forth in claim 1, wherein the second light guidelayer of the scattering light guide layer contains a light scatteringobject.
 5. The light guide plate as set forth in claim 1, wherein thescattering layer is constituted of depressions and projections formed ona surface of the second light guide layer, the surface being opposite toa surface in contact with the first light guide layer.
 6. The lightguide plate as set forth in claim 1, wherein the reflection means isdisposed so that light incident on the reflection means is reflected atan angle smaller than an angle shown by sin-1 (n2/n1), with respect to anormal direction to a surface on which the scattering light guide layeris formed.
 7. The light guide plate as set forth in claim 1, wherein thereflection means is a hologram.
 8. The light guide plate as set forth inclaim 1, wherein, the first light guide layer further includes on thesurface opposite to a surface on which the scattering light guide layeris formed, another scattering light guide layer.
 9. The light guideplate as set forth in claim 1, wherein the scattering light guide layerfurther includes a reflection member on a surface opposite to a surfaceon which the first light guide layer is formed.
 10. A lighting apparatuscomprising a light guide plate as set forth in claim 1, and a lightsource for irradiating the first light guide layer of the light guideplate with light.
 11. The lighting apparatus as set forth in claim 10,wherein the light source is so placed that an incident angle of thelight incident on the first light guide layer with respect to the lightguide surface of the first light guide layer falls in a predeterminedrange.
 12. The lighting apparatus as set forth in claim 11, wherein thelight source includes a light focusing optical element for focusing thelight incident on the first light guide layer of the light guide plate,so that the light is focused in a certain range of angles with respectto a stacking surface of the light guide plate.
 13. The lightingapparatus as set forth in claim 12, wherein the light focusing opticalelement is a cylindrical lens.
 14. The lighting apparatus as set forthin claim 10, wherein the light guide plate includes a plurality of thefirst light guide layer on the second light guide layer which are placedso that their light guide surfaces are opposed with a certain intervaltherebetween, and the light source is provided between the light guidesurfaces.
 15. The lighting apparatus as set forth in claim 10, furthercomprising a mirror for guiding the light from the light source to thefirst light guide layer.
 16. A flat light source apparatus comprising aplurality of the lighting apparatus as set forth in claim 10, thelighting apparatuses being placed side by side.
 17. The flat lightapparatus as set forth in claim 16, wherein reflection means of one oftwo lighting apparatuses is opposed to reflection means of anotherlighting apparatus.
 18. A display apparatus comprising the light guideplate as set forth in claim 1.